~drizzle-trunk/drizzle/development : contents of drizzled/sql

~drizzle-trunk/drizzle/development : (revision 960.2.20)
/* Copyright (C) 2000-2006 MySQL AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */


/* Basic functions needed by many modules */
#include <drizzled/server_includes.h>
#include <drizzled/virtual_column_info.h>
#include <drizzled/field/timestamp.h>
#include <drizzled/field/null.h>

#include <signal.h>

#if TIME_WITH_SYS_TIME
# include <sys/time.h>
# include <time.h>
#else
# if HAVE_SYS_TIME_H
#  include <sys/time.h>
# else
#  include <time.h>
# endif
#endif
#include <mysys/my_pthread.h>

#include <drizzled/sql_select.h>
#include <mysys/my_dir.h>
#include <drizzled/error.h>
#include <drizzled/gettext.h>
#include <drizzled/nested_join.h>
#include <drizzled/sql_base.h>
#include <drizzled/show.h>
#include <drizzled/item/cmpfunc.h>
#include <drizzled/replicator.h>
#include <drizzled/check_stack_overrun.h>
#include <drizzled/lock.h>


/**
  @defgroup Data_Dictionary Data Dictionary
  @{
*/
Table *unused_tables;				/* Used by mysql_test */
HASH open_cache;				/* Used by mysql_test */
static HASH table_def_cache;
static TABLE_SHARE *oldest_unused_share, end_of_unused_share;
static pthread_mutex_t LOCK_table_share;
static bool table_def_inited= 0;

static int open_unireg_entry(Session *session, Table *entry, TableList *table_list,
                             const char *alias,
                             char *cache_key, uint32_t cache_key_length);
extern "C" void free_cache_entry(void *entry);
static void close_old_data_files(Session *session, Table *table, bool morph_locks,
                                 bool send_refresh);


extern "C" unsigned char *table_cache_key(const unsigned char *record, size_t *length,
                                  bool )
{
  Table *entry=(Table*) record;
  *length= entry->s->table_cache_key.length;
  return (unsigned char*) entry->s->table_cache_key.str;
}


bool table_cache_init(void)
{
  return hash_init(&open_cache, &my_charset_bin,
                   (size_t) table_cache_size+16,
		   0, 0, table_cache_key,
		   free_cache_entry, 0);
}

void table_cache_free(void)
{
  if (table_def_inited)
  {
    close_cached_tables(NULL, NULL, false, false, false);
    if (!open_cache.records)			// Safety first
      hash_free(&open_cache);
  }
  return;
}

uint32_t cached_open_tables(void)
{
  return open_cache.records;
}

/*
  Create a table cache key

  SYNOPSIS
    create_table_def_key()
    session			Thread handler
    key			Create key here (must be of size MAX_DBKEY_LENGTH)
    table_list		Table definition
    tmp_table		Set if table is a tmp table

 IMPLEMENTATION
    The table cache_key is created from:
    db_name + \0
    table_name + \0

    if the table is a tmp table, we add the following to make each tmp table
    unique on the slave:

    4 bytes for master thread id
    4 bytes pseudo thread id

  RETURN
    Length of key
*/

uint32_t create_table_def_key(Session *session, char *key, TableList *table_list,
                          bool tmp_table)
{
  uint32_t key_length;
  char *key_pos= key;
  key_pos= strcpy(key_pos, table_list->db) + strlen(table_list->db);
  key_pos= strcpy(key_pos+1, table_list->table_name) +
                  strlen(table_list->table_name);
  key_length= (uint32_t)(key_pos-key)+1;

  if (tmp_table)
  {
    int4store(key + key_length, session->server_id);
    int4store(key + key_length + 4, session->variables.pseudo_thread_id);
    key_length+= TMP_TABLE_KEY_EXTRA;
  }
  return key_length;
}



/*****************************************************************************
  Functions to handle table definition cach (TABLE_SHARE)
*****************************************************************************/

extern "C" unsigned char *table_def_key(const unsigned char *record, size_t *length,
                                bool )
{
  TABLE_SHARE *entry=(TABLE_SHARE*) record;
  *length= entry->table_cache_key.length;
  return (unsigned char*) entry->table_cache_key.str;
}


static void table_def_free_entry(TABLE_SHARE *share)
{
  if (share->prev)
  {
    /* remove from old_unused_share list */
    pthread_mutex_lock(&LOCK_table_share);
    *share->prev= share->next;
    share->next->prev= share->prev;
    pthread_mutex_unlock(&LOCK_table_share);
  }
  free_table_share(share);
  return;
}


bool table_def_init(void)
{
  table_def_inited= 1;
  pthread_mutex_init(&LOCK_table_share, MY_MUTEX_INIT_FAST);
  oldest_unused_share= &end_of_unused_share;
  end_of_unused_share.prev= &oldest_unused_share;

  return hash_init(&table_def_cache, &my_charset_bin, (size_t)table_def_size,
		   0, 0, table_def_key,
		   (hash_free_key) table_def_free_entry, 0);
}


void table_def_free(void)
{
  if (table_def_inited)
  {
    table_def_inited= 0;
    pthread_mutex_destroy(&LOCK_table_share);
    hash_free(&table_def_cache);
  }
  return;
}


uint32_t cached_table_definitions(void)
{
  return table_def_cache.records;
}


/*
  Get TABLE_SHARE for a table.

  get_table_share()
  session			Thread handle
  table_list		Table that should be opened
  key			Table cache key
  key_length		Length of key
  db_flags		Flags to open_table_def():
			OPEN_VIEW
  error			out: Error code from open_table_def()

  IMPLEMENTATION
    Get a table definition from the table definition cache.
    If it doesn't exist, create a new from the table definition file.

  NOTES
    We must have wrlock on LOCK_open when we come here
    (To be changed later)

  RETURN
   0  Error
   #  Share for table
*/

TABLE_SHARE *get_table_share(Session *session, TableList *table_list, char *key,
                             uint32_t key_length, uint32_t db_flags, int *error)
{
  TABLE_SHARE *share;

  *error= 0;

  /* Read table definition from cache */
  if ((share= (TABLE_SHARE*) hash_search(&table_def_cache,(unsigned char*) key,
                                         key_length)))
    goto found;

  if (!(share= alloc_table_share(table_list, key, key_length)))
  {
    return(0);
  }

  /*
    Lock mutex to be able to read table definition from file without
    conflicts
  */
  (void) pthread_mutex_lock(&share->mutex);

  /*
    We assign a new table id under the protection of the LOCK_open and
    the share's own mutex.  We do this insted of creating a new mutex
    and using it for the sole purpose of serializing accesses to a
    static variable, we assign the table id here.  We assign it to the
    share before inserting it into the table_def_cache to be really
    sure that it cannot be read from the cache without having a table
    id assigned.

    CAVEAT. This means that the table cannot be used for
    binlogging/replication purposes, unless get_table_share() has been
    called directly or indirectly.
   */
  assign_new_table_id(share);

  if (my_hash_insert(&table_def_cache, (unsigned char*) share))
  {
    free_table_share(share);
    return(0);				// return error
  }
  if (open_table_def(session, share, db_flags))
  {
    *error= share->error;
    (void) hash_delete(&table_def_cache, (unsigned char*) share);
    return(0);
  }
  share->ref_count++;				// Mark in use
  (void) pthread_mutex_unlock(&share->mutex);
  return(share);

found:
  /*
     We found an existing table definition. Return it if we didn't get
     an error when reading the table definition from file.
  */

  /* We must do a lock to ensure that the structure is initialized */
  (void) pthread_mutex_lock(&share->mutex);
  if (share->error)
  {
    /* Table definition contained an error */
    open_table_error(share, share->error, share->open_errno, share->errarg);
    (void) pthread_mutex_unlock(&share->mutex);
    return(0);
  }

  if (!share->ref_count++ && share->prev)
  {
    /*
      Share was not used before and it was in the old_unused_share list
      Unlink share from this list
    */
    pthread_mutex_lock(&LOCK_table_share);
    *share->prev= share->next;
    share->next->prev= share->prev;
    share->next= 0;
    share->prev= 0;
    pthread_mutex_unlock(&LOCK_table_share);
  }
  (void) pthread_mutex_unlock(&share->mutex);

   /* Free cache if too big */
  while (table_def_cache.records > table_def_size &&
         oldest_unused_share->next)
  {
    pthread_mutex_lock(&oldest_unused_share->mutex);
    hash_delete(&table_def_cache, (unsigned char*) oldest_unused_share);
  }

  return(share);
}


/*
  Get a table share. If it didn't exist, try creating it from engine

  For arguments and return values, see get_table_from_share()
*/

static TABLE_SHARE
*get_table_share_with_create(Session *session, TableList *table_list,
                             char *key, uint32_t key_length,
                             uint32_t db_flags, int *error)
{
  TABLE_SHARE *share;

  share= get_table_share(session, table_list, key, key_length, db_flags, error);
  /*
    If share is not NULL, we found an existing share.

    If share is NULL, and there is no error, we're inside
    pre-locking, which silences 'ER_NO_SUCH_TABLE' errors
    with the intention to silently drop non-existing tables
    from the pre-locking list. In this case we still need to try
    auto-discover before returning a NULL share.

    If share is NULL and the error is ER_NO_SUCH_TABLE, this is
    the same as above, only that the error was not silenced by
    pre-locking. Once again, we need to try to auto-discover
    the share.

    Finally, if share is still NULL, it's a real error and we need
    to abort.

    @todo Rework alternative ways to deal with ER_NO_SUCH Table.
  */
  if (share || (session->is_error() && (session->main_da.sql_errno() != ER_NO_SUCH_TABLE)))

    return(share);

  return 0;
}


/*
   Mark that we are not using table share anymore.

   SYNOPSIS
     release_table_share()
     share		Table share
     release_type	How the release should be done:
     			RELEASE_NORMAL
                         - Release without checking
                        RELEASE_WAIT_FOR_DROP
                         - Don't return until we get a signal that the
                           table is deleted or the thread is killed.

   IMPLEMENTATION
     If ref_count goes to zero and (we have done a refresh or if we have
     already too many open table shares) then delete the definition.

     If type == RELEASE_WAIT_FOR_DROP then don't return until we get a signal
     that the table is deleted or the thread is killed.
*/

void release_table_share(TABLE_SHARE *share,
                         enum release_type )
{
  bool to_be_deleted= 0;

  safe_mutex_assert_owner(&LOCK_open);

  pthread_mutex_lock(&share->mutex);
  if (!--share->ref_count)
  {
    if (share->version != refresh_version)
      to_be_deleted=1;
    else
    {
      /* Link share last in used_table_share list */
      assert(share->next == 0);
      pthread_mutex_lock(&LOCK_table_share);
      share->prev= end_of_unused_share.prev;
      *end_of_unused_share.prev= share;
      end_of_unused_share.prev= &share->next;
      share->next= &end_of_unused_share;
      pthread_mutex_unlock(&LOCK_table_share);

      to_be_deleted= (table_def_cache.records > table_def_size);
    }
  }

  if (to_be_deleted)
  {
    hash_delete(&table_def_cache, (unsigned char*) share);
    return;
  }
  pthread_mutex_unlock(&share->mutex);
  return;
}


/*
  Check if table definition exits in cache

  SYNOPSIS
    get_cached_table_share()
    db			Database name
    table_name		Table name

  RETURN
    0  Not cached
    #  TABLE_SHARE for table
*/

TABLE_SHARE *get_cached_table_share(const char *db, const char *table_name)
{
  char key[NAME_LEN*2+2];
  TableList table_list;
  uint32_t key_length;
  safe_mutex_assert_owner(&LOCK_open);

  table_list.db= (char*) db;
  table_list.table_name= (char*) table_name;
  key_length= create_table_def_key((Session*) 0, key, &table_list, 0);
  return (TABLE_SHARE*) hash_search(&table_def_cache,(unsigned char*) key, key_length);
}


/*
  Close file handle, but leave the table in the table cache

  SYNOPSIS
    close_handle_and_leave_table_as_lock()
    table		Table handler

  NOTES
    By leaving the table in the table cache, it disallows any other thread
    to open the table

    session->killed will be set if we run out of memory

    If closing a MERGE child, the calling function has to take care for
    closing the parent too, if necessary.
*/


void close_handle_and_leave_table_as_lock(Table *table)
{
  TABLE_SHARE *share, *old_share= table->s;
  char *key_buff;
  MEM_ROOT *mem_root= &table->mem_root;

  assert(table->db_stat);

  /*
    Make a local copy of the table share and free the current one.
    This has to be done to ensure that the table share is removed from
    the table defintion cache as soon as the last instance is removed
  */
  if (multi_alloc_root(mem_root,
                       &share, sizeof(*share),
                       &key_buff, old_share->table_cache_key.length,
                       NULL))
  {
    memset(share, 0, sizeof(*share));
    share->set_table_cache_key(key_buff, old_share->table_cache_key.str,
                               old_share->table_cache_key.length);
    share->tmp_table= INTERNAL_TMP_TABLE;       // for intern_close_table()
  }

  table->file->close();
  table->db_stat= 0;                            // Mark file closed
  release_table_share(table->s, RELEASE_NORMAL);
  table->s= share;
  table->file->change_table_ptr(table, table->s);

  return;
}



/*
  Create a list for all open tables matching SQL expression

  SYNOPSIS
    list_open_tables()
    wild		SQL like expression

  NOTES
    One gets only a list of tables for which one has any kind of privilege.
    db and table names are allocated in result struct, so one doesn't need
    a lock on LOCK_open when traversing the return list.

  RETURN VALUES
    NULL	Error (Probably OOM)
    #		Pointer to list of names of open tables.
*/

OPEN_TableList *list_open_tables(const char *db, const char *wild)
{
  int result = 0;
  OPEN_TableList **start_list, *open_list;
  TableList table_list;

  pthread_mutex_lock(&LOCK_open);
  memset(&table_list, 0, sizeof(table_list));
  start_list= &open_list;
  open_list=0;

  for (uint32_t idx=0 ; result == 0 && idx < open_cache.records; idx++)
  {
    OPEN_TableList *table;
    Table *entry=(Table*) hash_element(&open_cache,idx);
    TABLE_SHARE *share= entry->s;

    if (db && my_strcasecmp(system_charset_info, db, share->db.str))
      continue;
    if (wild && wild_compare(share->table_name.str, wild, 0))
      continue;

    /* Check if user has SELECT privilege for any column in the table */
    table_list.db=         share->db.str;
    table_list.table_name= share->table_name.str;

    /* need to check if we haven't already listed it */
    for (table= open_list  ; table ; table=table->next)
    {
      if (!strcmp(table->table, share->table_name.str) &&
	  !strcmp(table->db,    share->db.str))
      {
	if (entry->in_use)
	  table->in_use++;
	if (entry->locked_by_name)
	  table->locked++;
	break;
      }
    }
    if (table)
      continue;
    if (!(*start_list = (OPEN_TableList *)
	  sql_alloc(sizeof(**start_list)+share->table_cache_key.length)))
    {
      open_list=0;				// Out of memory
      break;
    }
    strcpy((*start_list)->table=
           strcpy(((*start_list)->db= (char*) ((*start_list)+1)),
           share->db.str)+share->db.length+1,
           share->table_name.str);
    (*start_list)->in_use= entry->in_use ? 1 : 0;
    (*start_list)->locked= entry->locked_by_name ? 1 : 0;
    start_list= &(*start_list)->next;
    *start_list=0;
  }
  pthread_mutex_unlock(&LOCK_open);
  return(open_list);
}

/*****************************************************************************
 *	 Functions to free open table cache
 ****************************************************************************/


void intern_close_table(Table *table)
{						// Free all structures
  free_io_cache(table);
  if (table->file)                              // Not true if name lock
    table->closefrm(true);			// close file
  return;
}

/*
  Remove table from the open table cache

  SYNOPSIS
    free_cache_entry()
    entry		Table to remove

  NOTE
    We need to have a lock on LOCK_open when calling this
*/

void free_cache_entry(void *entry)
{
  Table *table= static_cast<Table *>(entry);
  intern_close_table(table);
  if (!table->in_use)
  {
    table->next->prev=table->prev;		/* remove from used chain */
    table->prev->next=table->next;
    if (table == unused_tables)
    {
      unused_tables=unused_tables->next;
      if (table == unused_tables)
	unused_tables=0;
    }
  }
  free(table);
  return;
}

/* Free resources allocated by filesort() and read_record() */

void free_io_cache(Table *table)
{
  if (table->sort.io_cache)
  {
    close_cached_file(table->sort.io_cache);
    delete table->sort.io_cache;
    table->sort.io_cache= 0;
  }
  return;
}


/*
  Close all tables which aren't in use by any thread

  @param session Thread context
  @param tables List of tables to remove from the cache
  @param have_lock If LOCK_open is locked
  @param wait_for_refresh Wait for a impending flush
  @param wait_for_placeholders Wait for tables being reopened so that the GRL
         won't proceed while write-locked tables are being reopened by other
         threads.

  @remark Session can be NULL, but then wait_for_refresh must be false
          and tables must be NULL.
*/

bool close_cached_tables(Session *session, TableList *tables, bool have_lock,
                         bool wait_for_refresh, bool wait_for_placeholders)
{
  bool result=0;
  assert(session || (!wait_for_refresh && !tables));

  if (!have_lock)
    pthread_mutex_lock(&LOCK_open);
  if (!tables)
  {
    refresh_version++;				// Force close of open tables
    while (unused_tables)
    {
#ifdef EXTRA_DEBUG
      if (hash_delete(&open_cache,(unsigned char*) unused_tables))
	printf("Warning: Couldn't delete open table from hash\n");
#else
      hash_delete(&open_cache,(unsigned char*) unused_tables);
#endif
    }
    /* Free table shares */
    while (oldest_unused_share->next)
    {
      pthread_mutex_lock(&oldest_unused_share->mutex);
      hash_delete(&table_def_cache, (unsigned char*) oldest_unused_share);
    }
    if (wait_for_refresh)
    {
      /*
        Other threads could wait in a loop in open_and_lock_tables(),
        trying to lock one or more of our tables.

        If they wait for the locks in thr_multi_lock(), their lock
        request is aborted. They loop in open_and_lock_tables() and
        enter open_table(). Here they notice the table is refreshed and
        wait for COND_refresh. Then they loop again in
        open_and_lock_tables() and this time open_table() succeeds. At
        this moment, if we (the FLUSH TABLES thread) are scheduled and
        on another FLUSH TABLES enter close_cached_tables(), they could
        awake while we sleep below, waiting for others threads (us) to
        close their open tables. If this happens, the other threads
        would find the tables unlocked. They would get the locks, one
        after the other, and could do their destructive work. This is an
        issue if we have LOCK TABLES in effect.

        The problem is that the other threads passed all checks in
        open_table() before we refresh the table.

        The fix for this problem is to set some_tables_deleted for all
        threads with open tables. These threads can still get their
        locks, but will immediately release them again after checking
        this variable. They will then loop in open_and_lock_tables()
        again. There they will wait until we update all tables version
        below.

        Setting some_tables_deleted is done by remove_table_from_cache()
        in the other branch.

        In other words (reviewer suggestion): You need this setting of
        some_tables_deleted for the case when table was opened and all
        related checks were passed before incrementing refresh_version
        (which you already have) but attempt to lock the table happened
        after the call to close_old_data_files() i.e. after removal of
        current thread locks.
      */
      for (uint32_t idx=0 ; idx < open_cache.records ; idx++)
      {
        Table *table=(Table*) hash_element(&open_cache,idx);
        if (table->in_use)
          table->in_use->some_tables_deleted= 1;
      }
    }
  }
  else
  {
    bool found=0;
    for (TableList *table= tables; table; table= table->next_local)
    {
      if (remove_table_from_cache(session, table->db, table->table_name,
                                  RTFC_OWNED_BY_Session_FLAG))
	found=1;
    }
    if (!found)
      wait_for_refresh=0;			// Nothing to wait for
  }

  if (wait_for_refresh)
  {
    /*
      If there is any table that has a lower refresh_version, wait until
      this is closed (or this thread is killed) before returning
    */
    session->mysys_var->current_mutex= &LOCK_open;
    session->mysys_var->current_cond= &COND_refresh;
    session->set_proc_info("Flushing tables");

    close_old_data_files(session,session->open_tables,1,1);

    bool found=1;
    /* Wait until all threads has closed all the tables we had locked */
    while (found && ! session->killed)
    {
      found=0;
      for (uint32_t idx=0 ; idx < open_cache.records ; idx++)
      {
	Table *table=(Table*) hash_element(&open_cache,idx);
        /* Avoid a self-deadlock. */
        if (table->in_use == session)
          continue;
        /*
          Note that we wait here only for tables which are actually open, and
          not for placeholders with Table::open_placeholder set. Waiting for
          latter will cause deadlock in the following scenario, for example:

          conn1: lock table t1 write;
          conn2: lock table t2 write;
          conn1: flush tables;
          conn2: flush tables;

          It also does not make sense to wait for those of placeholders that
          are employed by CREATE TABLE as in this case table simply does not
          exist yet.
        */
	if (table->needs_reopen_or_name_lock() && (table->db_stat ||
            (table->open_placeholder && wait_for_placeholders)))
	{
	  found=1;
	  pthread_cond_wait(&COND_refresh,&LOCK_open);
	  break;
	}
      }
    }
    /*
      No other thread has the locked tables open; reopen them and get the
      old locks. This should always succeed (unless some external process
      has removed the tables)
    */
    session->in_lock_tables=1;
    result=reopen_tables(session,1,1);
    session->in_lock_tables=0;
    /* Set version for table */
    for (Table *table=session->open_tables; table ; table= table->next)
    {
      /*
        Preserve the version (0) of write locked tables so that a impending
        global read lock won't sneak in.
      */
      if (table->reginfo.lock_type < TL_WRITE_ALLOW_WRITE)
        table->s->version= refresh_version;
    }
  }
  if (!have_lock)
    pthread_mutex_unlock(&LOCK_open);
  if (wait_for_refresh)
  {
    pthread_mutex_lock(&session->mysys_var->mutex);
    session->mysys_var->current_mutex= 0;
    session->mysys_var->current_cond= 0;
    session->set_proc_info(0);
    pthread_mutex_unlock(&session->mysys_var->mutex);
  }
  return(result);
}


/*
  Close all tables which match specified connection string or
  if specified string is NULL, then any table with a connection string.
*/

bool close_cached_connection_tables(Session *session, bool if_wait_for_refresh,
                                    LEX_STRING *connection, bool have_lock)
{
  uint32_t idx;
  TableList tmp, *tables= NULL;
  bool result= false;
  assert(session);

  memset(&tmp, 0, sizeof(TableList));

  if (!have_lock)
    pthread_mutex_lock(&LOCK_open);

  for (idx= 0; idx < table_def_cache.records; idx++)
  {
    TABLE_SHARE *share= (TABLE_SHARE *) hash_element(&table_def_cache, idx);

    /* Ignore if table is not open or does not have a connect_string */
    if (!share->connect_string.length || !share->ref_count)
      continue;

    /* Compare the connection string */
    if (connection &&
        (connection->length > share->connect_string.length ||
         (connection->length < share->connect_string.length &&
          (share->connect_string.str[connection->length] != '/' &&
           share->connect_string.str[connection->length] != '\\')) ||
         strncasecmp(connection->str, share->connect_string.str,
                     connection->length)))
      continue;

    /* close_cached_tables() only uses these elements */
    tmp.db= share->db.str;
    tmp.table_name= share->table_name.str;
    tmp.next_local= tables;

    tables= (TableList *) memdup_root(session->mem_root, (char*)&tmp,
                                       sizeof(TableList));
  }

  if (tables)
    result= close_cached_tables(session, tables, true, false, false);

  if (!have_lock)
    pthread_mutex_unlock(&LOCK_open);

  if (if_wait_for_refresh)
  {
    pthread_mutex_lock(&session->mysys_var->mutex);
    session->mysys_var->current_mutex= 0;
    session->mysys_var->current_cond= 0;
    session->set_proc_info(0);
    pthread_mutex_unlock(&session->mysys_var->mutex);
  }

  return(result);
}


/**
  Mark all temporary tables which were used by the current statement or
  substatement as free for reuse, but only if the query_id can be cleared.

  @param session thread context

  @remark For temp tables associated with a open SQL HANDLER the query_id
          is not reset until the HANDLER is closed.
*/

static void mark_temp_tables_as_free_for_reuse(Session *session)
{
  for (Table *table= session->temporary_tables ; table ; table= table->next)
  {
    if ((table->query_id == session->query_id) && ! table->open_by_handler)
    {
      table->query_id= 0;
      table->file->ha_reset();
    }
  }
}


/*
  Mark all tables in the list which were used by current substatement
  as free for reuse.

  SYNOPSIS
    mark_used_tables_as_free_for_reuse()
      session   - thread context
      table - head of the list of tables

  DESCRIPTION
    Marks all tables in the list which were used by current substatement
    (they are marked by its query_id) as free for reuse.

  NOTE
    The reason we reset query_id is that it's not enough to just test
    if table->query_id != session->query_id to know if a table is in use.

    For example
    SELECT f1_that_uses_t1() FROM t1;
    In f1_that_uses_t1() we will see one instance of t1 where query_id is
    set to query_id of original query.
*/

static void mark_used_tables_as_free_for_reuse(Session *session, Table *table)
{
  for (; table ; table= table->next)
  {
    if (table->query_id == session->query_id)
    {
      table->query_id= 0;
      table->file->ha_reset();
    }
  }
}


/**
  Auxiliary function to close all tables in the open_tables list.

  @param session Thread context.

  @remark It should not ordinarily be called directly.
*/

static void close_open_tables(Session *session)
{
  bool found_old_table= 0;

  safe_mutex_assert_not_owner(&LOCK_open);

  pthread_mutex_lock(&LOCK_open);

  while (session->open_tables)
    found_old_table|= close_thread_table(session, &session->open_tables);
  session->some_tables_deleted= 0;

  /* Free tables to hold down open files */
  while (open_cache.records > table_cache_size && unused_tables)
    hash_delete(&open_cache,(unsigned char*) unused_tables); /* purecov: tested */
  if (found_old_table)
  {
    /* Tell threads waiting for refresh that something has happened */
    broadcast_refresh();
  }

  pthread_mutex_unlock(&LOCK_open);
}


/*
  Close all tables used by the current substatement, or all tables
  used by this thread if we are on the upper level.

  SYNOPSIS
    close_thread_tables()
    session			Thread handler

  IMPLEMENTATION
    Unlocks tables and frees derived tables.
    Put all normal tables used by thread in free list.

    It will only close/mark as free for reuse tables opened by this
    substatement, it will also check if we are closing tables after
    execution of complete query (i.e. we are on upper level) and will
    leave prelocked mode if needed.
*/

void close_thread_tables(Session *session)
{
  Table *table;

  /*
    We are assuming here that session->derived_tables contains ONLY derived
    tables for this substatement. i.e. instead of approach which uses
    query_id matching for determining which of the derived tables belong
    to this substatement we rely on the ability of substatements to
    save/restore session->derived_tables during their execution.

    TODO: Probably even better approach is to simply associate list of
          derived tables with (sub-)statement instead of thread and destroy
          them at the end of its execution.
  */
  if (session->derived_tables)
  {
    Table *next;
    /*
      Close all derived tables generated in queries like
      SELECT * FROM (SELECT * FROM t1)
    */
    for (table= session->derived_tables ; table ; table= next)
    {
      next= table->next;
      table->free_tmp_table(session);
    }
    session->derived_tables= 0;
  }

  /*
    Mark all temporary tables used by this statement as free for reuse.
  */
  mark_temp_tables_as_free_for_reuse(session);
  /*
    Let us commit transaction for statement. Since in 5.0 we only have
    one statement transaction and don't allow several nested statement
    transactions this call will do nothing if we are inside of stored
    function or trigger (i.e. statement transaction is already active and
    does not belong to statement for which we do close_thread_tables()).
    TODO: This should be fixed in later releases.
   */
  if (!(session->state_flags & Open_tables_state::BACKUPS_AVAIL))
  {
    session->main_da.can_overwrite_status= true;
    ha_autocommit_or_rollback(session, session->is_error());
    session->main_da.can_overwrite_status= false;
    session->transaction.stmt.reset();
  }

  if (session->locked_tables)
  {

    /* Ensure we are calling ha_reset() for all used tables */
    mark_used_tables_as_free_for_reuse(session, session->open_tables);

    /*
      We are under simple LOCK TABLES so should not do anything else.
    */
    return;
  }

  if (session->lock)
  {
    /*
      For RBR we flush the pending event just before we unlock all the
      tables.  This means that we are at the end of a topmost
      statement, so we ensure that the STMT_END_F flag is set on the
      pending event.  For statements that are *inside* stored
      functions, the pending event will not be flushed: that will be
      handled either before writing a query log event (inside
      binlog_query()) or when preparing a pending event.
     */
    mysql_unlock_tables(session, session->lock);
    session->lock=0;
  }
  /*
    Note that we need to hold LOCK_open while changing the
    open_tables list. Another thread may work on it.
    (See: remove_table_from_cache(), mysql_wait_completed_table())
    Closing a MERGE child before the parent would be fatal if the
    other thread tries to abort the MERGE lock in between.
  */
  if (session->open_tables)
    close_open_tables(session);

  return;
}


/* move one table to free list */

bool close_thread_table(Session *session, Table **table_ptr)
{
  bool found_old_table= 0;
  Table *table= *table_ptr;

  assert(table->key_read == 0);
  assert(!table->file || table->file->inited == handler::NONE);

  *table_ptr=table->next;

  if (table->needs_reopen_or_name_lock() ||
      session->version != refresh_version || !table->db_stat)
  {
    hash_delete(&open_cache,(unsigned char*) table);
    found_old_table=1;
  }
  else
  {
    /*
      Open placeholders have Table::db_stat set to 0, so they should be
      handled by the first alternative.
    */
    assert(!table->open_placeholder);

    /* Free memory and reset for next loop */
    table->file->ha_reset();
    table->in_use=0;
    if (unused_tables)
    {
      table->next=unused_tables;		/* Link in last */
      table->prev=unused_tables->prev;
      unused_tables->prev=table;
      table->prev->next=table;
    }
    else
      unused_tables=table->next=table->prev=table;
  }
  return(found_old_table);
}

/*
  Find table in list.

  SYNOPSIS
    find_table_in_list()
    table		Pointer to table list
    offset		Offset to which list in table structure to use
    db_name		Data base name
    table_name		Table name

  NOTES:
    This is called by find_table_in_local_list() and
    find_table_in_global_list().

  RETURN VALUES
    NULL	Table not found
    #		Pointer to found table.
*/

TableList *find_table_in_list(TableList *table,
                               TableList *TableList::*link,
                               const char *db_name,
                               const char *table_name)
{
  for (; table; table= table->*link )
  {
    if ((table->table == 0 || table->table->s->tmp_table == NO_TMP_TABLE) &&
        strcmp(table->db, db_name) == 0 &&
        strcmp(table->table_name, table_name) == 0)
      break;
  }
  return table;
}


/*
  Test that table is unique (It's only exists once in the table list)

  SYNOPSIS
    unique_table()
    session                   thread handle
    table                 table which should be checked
    table_list            list of tables
    check_alias           whether to check tables' aliases

  NOTE: to exclude derived tables from check we use following mechanism:
    a) during derived table processing set Session::derived_tables_processing
    b) JOIN::prepare set SELECT::exclude_from_table_unique_test if
       Session::derived_tables_processing set. (we can't use JOIN::execute
       because for PS we perform only JOIN::prepare, but we can't set this
       flag in JOIN::prepare if we are not sure that we are in derived table
       processing loop, because multi-update call fix_fields() for some its
       items (which mean JOIN::prepare for subqueries) before unique_table
       call to detect which tables should be locked for write).
    c) unique_table skip all tables which belong to SELECT with
       SELECT::exclude_from_table_unique_test set.
    Also SELECT::exclude_from_table_unique_test used to exclude from check
    tables of main SELECT of multi-delete and multi-update

    We also skip tables with TableList::prelocking_placeholder set,
    because we want to allow SELECTs from them, and their modification
    will rise the error anyway.

    TODO: when we will have table/view change detection we can do this check
          only once for PS/SP

  RETURN
    found duplicate
    0 if table is unique
*/

TableList* unique_table(Session *session, TableList *table, TableList *table_list,
                         bool check_alias)
{
  TableList *res;
  const char *d_name, *t_name, *t_alias;

  /*
    If this function called for query which update table (INSERT/UPDATE/...)
    then we have in table->table pointer to Table object which we are
    updating even if it is VIEW so we need TableList of this Table object
    to get right names (even if lower_case_table_names used).

    If this function called for CREATE command that we have not opened table
    (table->table equal to 0) and right names is in current TableList
    object.
  */
  if (table->table)
  {
    /* temporary table is always unique */
    if (table->table && table->table->s->tmp_table != NO_TMP_TABLE)
      return(0);
    table= table->find_underlying_table(table->table);
    /*
      as far as we have table->table we have to find real TableList of
      it in underlying tables
    */
    assert(table);
  }
  d_name= table->db;
  t_name= table->table_name;
  t_alias= table->alias;

  for (;;)
  {
    if (((! (res= find_table_in_global_list(table_list, d_name, t_name))) &&
         (! (res= mysql_lock_have_duplicate(session, table, table_list)))) ||
        ((!res->table || res->table != table->table) &&
         (!check_alias || !(lower_case_table_names ?
          my_strcasecmp(files_charset_info, t_alias, res->alias) :
          strcmp(t_alias, res->alias))) &&
         res->select_lex && !res->select_lex->exclude_from_table_unique_test))
      break;
    /*
      If we found entry of this table or table of SELECT which already
      processed in derived table or top select of multi-update/multi-delete
      (exclude_from_table_unique_test) or prelocking placeholder.
    */
    table_list= res->next_global;
  }
  return(res);
}


/*
  Issue correct error message in case we found 2 duplicate tables which
  prevent some update operation

  SYNOPSIS
    update_non_unique_table_error()
    update      table which we try to update
    operation   name of update operation
    duplicate   duplicate table which we found

  NOTE:
    here we hide view underlying tables if we have them
*/

void update_non_unique_table_error(TableList *update,
                                   const char *,
                                   TableList *)
{
  my_error(ER_UPDATE_TABLE_USED, MYF(0), update->alias);
}


Table *find_temporary_table(Session *session, const char *db, const char *table_name)
{
  TableList table_list;

  table_list.db= (char*) db;
  table_list.table_name= (char*) table_name;
  return find_temporary_table(session, &table_list);
}


Table *find_temporary_table(Session *session, TableList *table_list)
{
  char	key[MAX_DBKEY_LENGTH];
  uint	key_length;
  Table *table;

  key_length= create_table_def_key(session, key, table_list, 1);
  for (table=session->temporary_tables ; table ; table= table->next)
  {
    if (table->s->table_cache_key.length == key_length &&
	!memcmp(table->s->table_cache_key.str, key, key_length))
      return(table);
  }
  return(0);                               // Not a temporary table
}


/**
  Drop a temporary table.

  Try to locate the table in the list of session->temporary_tables.
  If the table is found:
   - if the table is being used by some outer statement, fail.
   - if the table is in session->locked_tables, unlock it and
     remove it from the list of locked tables. Currently only transactional
     temporary tables are present in the locked_tables list.
   - Close the temporary table, remove its .FRM
   - remove the table from the list of temporary tables

  This function is used to drop user temporary tables, as well as
  internal tables created in CREATE TEMPORARY TABLE ... SELECT
  or ALTER Table. Even though part of the work done by this function
  is redundant when the table is internal, as long as we
  link both internal and user temporary tables into the same
  session->temporary_tables list, it's impossible to tell here whether
  we're dealing with an internal or a user temporary table.

  @retval  0  the table was found and dropped successfully.
  @retval  1  the table was not found in the list of temporary tables
              of this thread
  @retval -1  the table is in use by a outer query
*/

int drop_temporary_table(Session *session, TableList *table_list)
{
  Table *table;

  if (!(table= find_temporary_table(session, table_list)))
    return(1);

  /* Table might be in use by some outer statement. */
  if (table->query_id && table->query_id != session->query_id)
  {
    my_error(ER_CANT_REOPEN_TABLE, MYF(0), table->alias);
    return(-1);
  }

  /*
    If LOCK TABLES list is not empty and contains this table,
    unlock the table and remove the table from this list.
  */
  mysql_lock_remove(session, session->locked_tables, table, false);
  close_temporary_table(session, table, 1, 1);
  return(0);
}

/*
  unlink from session->temporary tables and close temporary table
*/

void close_temporary_table(Session *session, Table *table,
                           bool free_share, bool delete_table)
{
  if (table->prev)
  {
    table->prev->next= table->next;
    if (table->prev->next)
      table->next->prev= table->prev;
  }
  else
  {
    /* removing the item from the list */
    assert(table == session->temporary_tables);
    /*
      slave must reset its temporary list pointer to zero to exclude
      passing non-zero value to end_slave via rli->save_temporary_tables
      when no temp tables opened, see an invariant below.
    */
    session->temporary_tables= table->next;
    if (session->temporary_tables)
      table->next->prev= 0;
  }
  close_temporary(table, free_share, delete_table);
  return;
}


/*
  Close and delete a temporary table

  NOTE
    This dosn't unlink table from session->temporary
    If this is needed, use close_temporary_table()
*/

void close_temporary(Table *table, bool free_share, bool delete_table)
{
  handlerton *table_type= table->s->db_type();

  free_io_cache(table);
  table->closefrm(false);

  if (delete_table)
    rm_temporary_table(table_type, table->s->path.str);

  if (free_share)
  {
    free_table_share(table->s);
    free((char*) table);
  }
  return;
}


/*
  Used by ALTER Table when the table is a temporary one. It changes something
  only if the ALTER contained a RENAME clause (otherwise, table_name is the old
  name).
  Prepares a table cache key, which is the concatenation of db, table_name and
  session->slave_proxy_id, separated by '\0'.
*/

bool rename_temporary_table(Session* session, Table *table, const char *db,
			    const char *table_name)
{
  char *key;
  uint32_t key_length;
  TABLE_SHARE *share= table->s;
  TableList table_list;

  if (!(key=(char*) alloc_root(&share->mem_root, MAX_DBKEY_LENGTH)))
    return true;				/* purecov: inspected */

  table_list.db= (char*) db;
  table_list.table_name= (char*) table_name;
  key_length= create_table_def_key(session, key, &table_list, 1);
  share->set_table_cache_key(key, key_length);

  return false;
}


	/* move table first in unused links */

static void relink_unused(Table *table)
{
  if (table != unused_tables)
  {
    table->prev->next=table->next;		/* Remove from unused list */
    table->next->prev=table->prev;
    table->next=unused_tables;			/* Link in unused tables */
    table->prev=unused_tables->prev;
    unused_tables->prev->next=table;
    unused_tables->prev=table;
    unused_tables=table;
  }
}


/**
    Remove all instances of table from thread's open list and
    table cache.

    @param  session     Thread context
    @param  find    Table to remove
    @param  unlock  true  - free all locks on tables removed that are
                            done with LOCK TABLES
                    false - otherwise

    @note When unlock parameter is false or current thread doesn't have
          any tables locked with LOCK TABLES, tables are assumed to be
          not locked (for example already unlocked).
*/

void unlink_open_table(Session *session, Table *find, bool unlock)
{
  char key[MAX_DBKEY_LENGTH];
  uint32_t key_length= find->s->table_cache_key.length;
  Table *list, **prev;

  safe_mutex_assert_owner(&LOCK_open);

  memcpy(key, find->s->table_cache_key.str, key_length);
  /*
    Note that we need to hold LOCK_open while changing the
    open_tables list. Another thread may work on it.
    (See: remove_table_from_cache(), mysql_wait_completed_table())
    Closing a MERGE child before the parent would be fatal if the
    other thread tries to abort the MERGE lock in between.
  */
  for (prev= &session->open_tables; *prev; )
  {
    list= *prev;

    if (list->s->table_cache_key.length == key_length &&
	!memcmp(list->s->table_cache_key.str, key, key_length))
    {
      if (unlock && session->locked_tables)
        mysql_lock_remove(session, session->locked_tables, list, true);

      /* Remove table from open_tables list. */
      *prev= list->next;
      /* Close table. */
      hash_delete(&open_cache,(unsigned char*) list); // Close table
    }
    else
    {
      /* Step to next entry in open_tables list. */
      prev= &list->next;
    }
  }

  // Notify any 'refresh' threads
  broadcast_refresh();
  return;
}


/**
    Auxiliary routine which closes and drops open table.

    @param  session         Thread handle
    @param  table       Table object for table to be dropped
    @param  db_name     Name of database for this table
    @param  table_name  Name of this table

    @note This routine assumes that table to be closed is open only
          by calling thread so we needn't wait until other threads
          will close the table. Also unless called under implicit or
          explicit LOCK TABLES mode it assumes that table to be
          dropped is already unlocked. In the former case it will
          also remove lock on the table. But one should not rely on
          this behaviour as it may change in future.
          Currently, however, this function is never called for a
          table that was locked with LOCK TABLES.
*/

void drop_open_table(Session *session, Table *table, const char *db_name,
                     const char *table_name)
{
  if (table->s->tmp_table)
    close_temporary_table(session, table, 1, 1);
  else
  {
    handlerton *table_type= table->s->db_type();
    pthread_mutex_lock(&LOCK_open);
    /*
      unlink_open_table() also tells threads waiting for refresh or close
      that something has happened.
    */
    unlink_open_table(session, table, false);
    quick_rm_table(table_type, db_name, table_name, 0);
    pthread_mutex_unlock(&LOCK_open);
  }
}


/*
   Wait for condition but allow the user to send a kill to mysqld

   SYNOPSIS
     wait_for_condition()
     session	Thread handler
     mutex	mutex that is currently hold that is associated with condition
	        Will be unlocked on return
     cond	Condition to wait for
*/

void wait_for_condition(Session *session, pthread_mutex_t *mutex, pthread_cond_t *cond)
{
  /* Wait until the current table is up to date */
  const char *proc_info;
  session->mysys_var->current_mutex= mutex;
  session->mysys_var->current_cond= cond;
  proc_info=session->get_proc_info();
  session->set_proc_info("Waiting for table");
  if (!session->killed)
    (void) pthread_cond_wait(cond, mutex);

  /*
    We must unlock mutex first to avoid deadlock becasue conditions are
    sent to this thread by doing locks in the following order:
    lock(mysys_var->mutex)
    lock(mysys_var->current_mutex)

    One by effect of this that one can only use wait_for_condition with
    condition variables that are guranteed to not disapper (freed) even if this
    mutex is unlocked
  */

  pthread_mutex_unlock(mutex);
  pthread_mutex_lock(&session->mysys_var->mutex);
  session->mysys_var->current_mutex= 0;
  session->mysys_var->current_cond= 0;
  session->set_proc_info(proc_info);
  pthread_mutex_unlock(&session->mysys_var->mutex);
  return;
}


/**
  Exclusively name-lock a table that is already write-locked by the
  current thread.

  @param session current thread context
  @param tables table list containing one table to open.

  @return false on success, true otherwise.
*/

bool name_lock_locked_table(Session *session, TableList *tables)
{
  /* Under LOCK TABLES we must only accept write locked tables. */
  tables->table= find_locked_table(session, tables->db, tables->table_name);

  if (!tables->table)
    my_error(ER_TABLE_NOT_LOCKED, MYF(0), tables->alias);
  else if (tables->table->reginfo.lock_type < TL_WRITE_LOW_PRIORITY)
    my_error(ER_TABLE_NOT_LOCKED_FOR_WRITE, MYF(0), tables->alias);
  else
  {
    /*
      Ensures that table is opened only by this thread and that no
      other statement will open this table.
    */
    wait_while_table_is_used(session, tables->table, HA_EXTRA_FORCE_REOPEN);
    return(false);
  }

  return(true);
}


/*
  Open table which is already name-locked by this thread.

  SYNOPSIS
    reopen_name_locked_table()
      session         Thread handle
      table_list  TableList object for table to be open, TableList::table
                  member should point to Table object which was used for
                  name-locking.
      link_in     true  - if Table object for table to be opened should be
                          linked into Session::open_tables list.
                  false - placeholder used for name-locking is already in
                          this list so we only need to preserve Table::next
                          pointer.

  NOTE
    This function assumes that its caller already acquired LOCK_open mutex.

  RETURN VALUE
    false - Success
    true  - Error
*/

bool reopen_name_locked_table(Session* session, TableList* table_list, bool link_in)
{
  Table *table= table_list->table;
  TABLE_SHARE *share;
  char *table_name= table_list->table_name;
  Table orig_table;

  safe_mutex_assert_owner(&LOCK_open);

  if (session->killed || !table)
    return(true);

  orig_table= *table;

  if (open_unireg_entry(session, table, table_list, table_name,
                        table->s->table_cache_key.str,
                        table->s->table_cache_key.length))
  {
    intern_close_table(table);
    /*
      If there was an error during opening of table (for example if it
      does not exist) '*table' object can be wiped out. To be able
      properly release name-lock in this case we should restore this
      object to its original state.
    */
    *table= orig_table;
    return(true);
  }

  share= table->s;
  /*
    We want to prevent other connections from opening this table until end
    of statement as it is likely that modifications of table's metadata are
    not yet finished (for example CREATE TRIGGER have to change .TRG file,
    or we might want to drop table if CREATE TABLE ... SELECT fails).
    This also allows us to assume that no other connection will sneak in
    before we will get table-level lock on this table.
  */
  share->version=0;
  table->in_use = session;

  if (link_in)
  {
    table->next= session->open_tables;
    session->open_tables= table;
  }
  else
  {
    /*
      Table object should be already in Session::open_tables list so we just
      need to set Table::next correctly.
    */
    table->next= orig_table.next;
  }

  table->tablenr=session->current_tablenr++;
  table->used_fields=0;
  table->const_table=0;
  table->null_row= false;
  table->maybe_null= false;
  table->force_index= false;
  table->status=STATUS_NO_RECORD;
  return false;
}


/**
    Create and insert into table cache placeholder for table
    which will prevent its opening (or creation) (a.k.a lock
    table name).

    @param session         Thread context
    @param key         Table cache key for name to be locked
    @param key_length  Table cache key length

    @return Pointer to Table object used for name locking or 0 in
            case of failure.
*/

Table *table_cache_insert_placeholder(Session *session, const char *key,
                                      uint32_t key_length)
{
  Table *table;
  TABLE_SHARE *share;
  char *key_buff;

  safe_mutex_assert_owner(&LOCK_open);

  /*
    Create a table entry with the right key and with an old refresh version
    Note that we must use my_multi_malloc() here as this is freed by the
    table cache
  */
  if (!my_multi_malloc(MYF(MY_WME | MY_ZEROFILL),
                       &table, sizeof(*table),
                       &share, sizeof(*share),
                       &key_buff, key_length,
                       NULL))
    return(NULL);

  table->s= share;
  share->set_table_cache_key(key_buff, key, key_length);
  share->tmp_table= INTERNAL_TMP_TABLE;  // for intern_close_table
  table->in_use= session;
  table->locked_by_name=1;

  if (my_hash_insert(&open_cache, (unsigned char*)table))
  {
    free((unsigned char*) table);
    return(NULL);
  }

  return(table);
}


/**
    Obtain an exclusive name lock on the table if it is not cached
    in the table cache.

    @param      session         Thread context
    @param      db          Name of database
    @param      table_name  Name of table
    @param[out] table       Out parameter which is either:
                            - set to NULL if table cache contains record for
                              the table or
                            - set to point to the Table instance used for
                              name-locking.

    @note This function takes into account all records for table in table
          cache, even placeholders used for name-locking. This means that
          'table' parameter can be set to NULL for some situations when
          table does not really exist.

    @retval  true   Error occured (OOM)
    @retval  false  Success. 'table' parameter set according to above rules.
*/

bool lock_table_name_if_not_cached(Session *session, const char *db,
                                   const char *table_name, Table **table)
{
  char key[MAX_DBKEY_LENGTH];
  char *key_pos= key;
  uint32_t key_length;

  key_pos= strcpy(key_pos, db) + strlen(db);
  key_pos= strcpy(key_pos+1, table_name) + strlen(table_name);
  key_length= (uint32_t) (key_pos-key)+1;

  pthread_mutex_lock(&LOCK_open);

  if (hash_search(&open_cache, (unsigned char *)key, key_length))
  {
    pthread_mutex_unlock(&LOCK_open);
    *table= 0;
    return(false);
  }
  if (!(*table= table_cache_insert_placeholder(session, key, key_length)))
  {
    pthread_mutex_unlock(&LOCK_open);
    return(true);
  }
  (*table)->open_placeholder= 1;
  (*table)->next= session->open_tables;
  session->open_tables= *table;
  pthread_mutex_unlock(&LOCK_open);
  return(false);
}

/*
  Open a table.

  SYNOPSIS
    open_table()
    session                 Thread context.
    table_list          Open first table in list.
    refresh      INOUT  Pointer to memory that will be set to 1 if
                        we need to close all tables and reopen them.
                        If this is a NULL pointer, then the table is not
                        put in the thread-open-list.
    flags               Bitmap of flags to modify how open works:
                          DRIZZLE_LOCK_IGNORE_FLUSH - Open table even if
                          someone has done a flush or namelock on it.
                          No version number checking is done.
                          DRIZZLE_OPEN_TEMPORARY_ONLY - Open only temporary
                          table not the base table or view.

  IMPLEMENTATION
    Uses a cache of open tables to find a table not in use.

    If table list element for the table to be opened has "create" flag
    set and table does not exist, this function will automatically insert
    a placeholder for exclusive name lock into the open tables cache and
    will return the Table instance that corresponds to this placeholder.

  RETURN
    NULL  Open failed.  If refresh is set then one should close
          all other tables and retry the open.
    #     Success. Pointer to Table object for open table.
*/


Table *open_table(Session *session, TableList *table_list, bool *refresh, uint32_t flags)
{
  register Table *table;
  char key[MAX_DBKEY_LENGTH];
  unsigned int key_length;
  char *alias= table_list->alias;
  HASH_SEARCH_STATE state;

  /* Parsing of partitioning information from .frm needs session->lex set up. */
  assert(session->lex->is_lex_started);

  /* find a unused table in the open table cache */
  if (refresh)
    *refresh=0;

  /* an open table operation needs a lot of the stack space */
  if (check_stack_overrun(session, STACK_MIN_SIZE_FOR_OPEN, (unsigned char *)&alias))
    return(0);

  if (session->killed)
    return(0);

  key_length= (create_table_def_key(session, key, table_list, 1) -
               TMP_TABLE_KEY_EXTRA);

  /*
    Unless requested otherwise, try to resolve this table in the list
    of temporary tables of this thread. In MySQL temporary tables
    are always thread-local and "shadow" possible base tables with the
    same name. This block implements the behaviour.
    TODO: move this block into a separate function.
  */
  {
    for (table= session->temporary_tables; table ; table=table->next)
    {
      if (table->s->table_cache_key.length == key_length +
          TMP_TABLE_KEY_EXTRA && !memcmp(table->s->table_cache_key.str, key,
          key_length + TMP_TABLE_KEY_EXTRA))
      {
        /*
          We're trying to use the same temporary table twice in a query.
          Right now we don't support this because a temporary table
          is always represented by only one Table object in Session, and
          it can not be cloned. Emit an error for an unsupported behaviour.
        */
        if (table->query_id)
        {
          my_error(ER_CANT_REOPEN_TABLE, MYF(0), table->alias);
          return(0);
        }
        table->query_id= session->query_id;
        session->thread_specific_used= true;
        goto reset;
      }
    }
  }

  if (flags & DRIZZLE_OPEN_TEMPORARY_ONLY)
  {
    my_error(ER_NO_SUCH_TABLE, MYF(0), table_list->db, table_list->table_name);
    return(0);
  }

  /*
    The table is not temporary - if we're in pre-locked or LOCK TABLES
    mode, let's try to find the requested table in the list of pre-opened
    and locked tables. If the table is not there, return an error - we can't
    open not pre-opened tables in pre-locked/LOCK TABLES mode.
    TODO: move this block into a separate function.
  */
  if (session->locked_tables)
  { // Using table locks
    Table *best_table= 0;
    int best_distance= INT_MIN;
    bool check_if_used= false;
    for (table=session->open_tables; table ; table=table->next)
    {
      if (table->s->table_cache_key.length == key_length &&
          !memcmp(table->s->table_cache_key.str, key, key_length))
      {
        if (check_if_used && table->query_id &&
            table->query_id != session->query_id)
        {
          /*
            If we are in stored function or trigger we should ensure that
            we won't change table that is already used by calling statement.
            So if we are opening table for writing, we should check that it
            is not already open by some calling stamement.
          */
          my_error(ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG, MYF(0),
                   table->s->table_name.str);
          return(0);
        }
        /*
          When looking for a usable Table, ignore MERGE children, as they
          belong to their parent and cannot be used explicitly.
        */
        if (!my_strcasecmp(system_charset_info, table->alias, alias) &&
            table->query_id != session->query_id)  /* skip tables already used */
        {
          int distance= ((int) table->reginfo.lock_type -
                         (int) table_list->lock_type);
          /*
            Find a table that either has the exact lock type requested,
            or has the best suitable lock. In case there is no locked
            table that has an equal or higher lock than requested,
            we us the closest matching lock to be able to produce an error
            message about wrong lock mode on the table. The best_table
            is changed if bd < 0 <= d or bd < d < 0 or 0 <= d < bd.

            distance <  0 - No suitable lock found
            distance >  0 - we have lock mode higher then we require
            distance == 0 - we have lock mode exactly which we need
          */
          if ((best_distance < 0 && distance > best_distance) || (distance >= 0 && distance < best_distance))
          {
            best_distance= distance;
            best_table= table;
            if (best_distance == 0 && !check_if_used)
            {
              /*
                If we have found perfect match and we don't need to check that
                table is not used by one of calling statements (assuming that
                we are inside of function or trigger) we can finish iterating
                through open tables list.
              */
              break;
            }
          }
        }
      }
    }
    if (best_table)
    {
      table= best_table;
      table->query_id= session->query_id;
      goto reset;
    }
    /*
      No table in the locked tables list. In case of explicit LOCK TABLES
      this can happen if a user did not include the able into the list.
      In case of pre-locked mode locked tables list is generated automatically,
      so we may only end up here if the table did not exist when
      locked tables list was created.
    */
    my_error(ER_TABLE_NOT_LOCKED, MYF(0), alias);
    return(0);
  }

  /*
    Non pre-locked/LOCK TABLES mode, and the table is not temporary:
    this is the normal use case.
    Now we should:
    - try to find the table in the table cache.
    - if one of the discovered Table instances is name-locked
      (table->s->version == 0) or some thread has started FLUSH TABLES
      (refresh_version > table->s->version), back off -- we have to wait
      until no one holds a name lock on the table.
    - if there is no such Table in the name cache, read the table definition
    and insert it into the cache.
    We perform all of the above under LOCK_open which currently protects
    the open cache (also known as table cache) and table definitions stored
    on disk.
  */

  pthread_mutex_lock(&LOCK_open);

  /*
    If it's the first table from a list of tables used in a query,
    remember refresh_version (the version of open_cache state).
    If the version changes while we're opening the remaining tables,
    we will have to back off, close all the tables opened-so-far,
    and try to reopen them.
    Note: refresh_version is currently changed only during FLUSH TABLES.
  */
  if (!session->open_tables)
    session->version=refresh_version;
  else if ((session->version != refresh_version) &&
           ! (flags & DRIZZLE_LOCK_IGNORE_FLUSH))
  {
    /* Someone did a refresh while thread was opening tables */
    if (refresh)
      *refresh=1;
    pthread_mutex_unlock(&LOCK_open);
    return(0);
  }

  /*
    Actually try to find the table in the open_cache.
    The cache may contain several "Table" instances for the same
    physical table. The instances that are currently "in use" by
    some thread have their "in_use" member != NULL.
    There is no good reason for having more than one entry in the
    hash for the same physical table, except that we use this as
    an implicit "pending locks queue" - see
    wait_for_locked_table_names for details.
  */
  for (table= (Table*) hash_first(&open_cache, (unsigned char*) key, key_length,
                                  &state);
       table && table->in_use ;
       table= (Table*) hash_next(&open_cache, (unsigned char*) key, key_length,
                                 &state))
  {
    /*
      Here we flush tables marked for flush.
      Normally, table->s->version contains the value of
      refresh_version from the moment when this table was
      (re-)opened and added to the cache.
      If since then we did (or just started) FLUSH TABLES
      statement, refresh_version has been increased.
      For "name-locked" Table instances, table->s->version is set
      to 0 (see lock_table_name for details).
      In case there is a pending FLUSH TABLES or a name lock, we
      need to back off and re-start opening tables.
      If we do not back off now, we may dead lock in case of lock
      order mismatch with some other thread:
      c1: name lock t1; -- sort of exclusive lock
      c2: open t2;      -- sort of shared lock
      c1: name lock t2; -- blocks
      c2: open t1; -- blocks
    */
    if (table->needs_reopen_or_name_lock())
    {
      if (flags & DRIZZLE_LOCK_IGNORE_FLUSH)
      {
        /* Force close at once after usage */
        session->version= table->s->version;
        continue;
      }

      /* Avoid self-deadlocks by detecting self-dependencies. */
      if (table->open_placeholder && table->in_use == session)
      {
        pthread_mutex_unlock(&LOCK_open);
        my_error(ER_UPDATE_TABLE_USED, MYF(0), table->s->table_name.str);
        return(0);
      }

      /*
        Back off, part 1: mark the table as "unused" for the
        purpose of name-locking by setting table->db_stat to 0. Do
        that only for the tables in this thread that have an old
        table->s->version (this is an optimization (?)).
        table->db_stat == 0 signals wait_for_locked_table_names
        that the tables in question are not used any more. See
        table_is_used call for details.

        Notice that HANDLER tables were already taken care of by
        the earlier call to mysql_ha_flush() in this same critical
        section.
      */
      close_old_data_files(session,session->open_tables,0,0);
      /*
        Back-off part 2: try to avoid "busy waiting" on the table:
        if the table is in use by some other thread, we suspend
        and wait till the operation is complete: when any
        operation that juggles with table->s->version completes,
        it broadcasts COND_refresh condition variable.
        If 'old' table we met is in use by current thread we return
        without waiting since in this situation it's this thread
        which is responsible for broadcasting on COND_refresh
        (and this was done already in close_old_data_files()).
        Good example of such situation is when we have statement
        that needs two instances of table and FLUSH TABLES comes
        after we open first instance but before we open second
        instance.
      */
      if (table->in_use != session)
      {
        /* wait_for_conditionwill unlock LOCK_open for us */
        wait_for_condition(session, &LOCK_open, &COND_refresh);
      }
      else
      {
        pthread_mutex_unlock(&LOCK_open);
      }
      /*
        There is a refresh in progress for this table.
        Signal the caller that it has to try again.
      */
      if (refresh)
        *refresh=1;
      return(0);
    }
  }
  if (table)
  {
    /* Unlink the table from "unused_tables" list. */
    if (table == unused_tables)
    {  // First unused
      unused_tables=unused_tables->next; // Remove from link
      if (table == unused_tables)
        unused_tables=0;
    }
    table->prev->next=table->next; /* Remove from unused list */
    table->next->prev=table->prev;
    table->in_use= session;
  }
  else
  {
    /* Insert a new Table instance into the open cache */
    int error;
    /* Free cache if too big */
    while (open_cache.records > table_cache_size && unused_tables)
      hash_delete(&open_cache,(unsigned char*) unused_tables); /* purecov: tested */

    if (table_list->create)
    {
      if(ha_table_exists_in_engine(session, table_list->db,
                                   table_list->table_name)
         != HA_ERR_TABLE_EXIST)
      {
        /*
          Table to be created, so we need to create placeholder in table-cache.
        */
        if (!(table= table_cache_insert_placeholder(session, key, key_length)))
        {
          pthread_mutex_unlock(&LOCK_open);
          return(NULL);
        }
        /*
          Link placeholder to the open tables list so it will be automatically
          removed once tables are closed. Also mark it so it won't be ignored
          by other trying to take name-lock.
        */
        table->open_placeholder= 1;
        table->next= session->open_tables;
        session->open_tables= table;
        pthread_mutex_unlock(&LOCK_open);
        return(table);
      }
      /* Table exists. Let us try to open it. */
    }

    /* make a new table */
    table= (Table *) malloc(sizeof(*table));
    if (table == NULL)
    {
      pthread_mutex_unlock(&LOCK_open);
      return(NULL);
    }

    error= open_unireg_entry(session, table, table_list, alias, key, key_length);
    if (error != 0)
    {
      free(table);
      pthread_mutex_unlock(&LOCK_open);
      return(NULL);
    }
    my_hash_insert(&open_cache,(unsigned char*) table);
  }

  pthread_mutex_unlock(&LOCK_open);
  if (refresh)
  {
    table->next=session->open_tables; /* Link into simple list */
    session->open_tables=table;
  }
  table->reginfo.lock_type=TL_READ; /* Assume read */

 reset:
  assert(table->s->ref_count > 0 || table->s->tmp_table != NO_TMP_TABLE);

  if (session->lex->need_correct_ident())
    table->alias_name_used= my_strcasecmp(table_alias_charset,
                                          table->s->table_name.str, alias);
  /* Fix alias if table name changes */
  if (strcmp(table->alias, alias))
  {
    uint32_t length=(uint32_t) strlen(alias)+1;
    table->alias= (char*) realloc((char*) table->alias, length);
    memcpy((void*) table->alias, alias, length);
  }
  /* These variables are also set in reopen_table() */
  table->tablenr=session->current_tablenr++;
  table->used_fields=0;
  table->const_table=0;
  table->null_row= false;
  table->maybe_null= false;
  table->force_index= false;
  table->status=STATUS_NO_RECORD;
  table->insert_values= 0;
  /* Catch wrong handling of the auto_increment_field_not_null. */
  assert(!table->auto_increment_field_not_null);
  table->auto_increment_field_not_null= false;
  if (table->timestamp_field)
    table->timestamp_field_type= table->timestamp_field->get_auto_set_type();
  table->pos_in_table_list= table_list;
  table->clear_column_bitmaps();
  assert(table->key_read == 0);
  return(table);
}


Table *find_locked_table(Session *session, const char *db,const char *table_name)
{
  char key[MAX_DBKEY_LENGTH];
  char *key_pos= key;
  uint32_t key_length;

  key_pos= strcpy(key_pos, db) + strlen(db);
  key_pos= strcpy(key_pos+1, table_name) + strlen(table_name);
  key_length= (uint32_t)(key_pos-key)+1;

  for (Table *table=session->open_tables; table ; table=table->next)
  {
    if (table->s->table_cache_key.length == key_length &&
        !memcmp(table->s->table_cache_key.str, key, key_length))
      return table;
  }
  return(0);
}


/*
  Reopen an table because the definition has changed.

  SYNOPSIS
    reopen_table()
    table	Table object

  NOTES
   The data file for the table is already closed and the share is released
   The table has a 'dummy' share that mainly contains database and table name.

 RETURN
   0  ok
   1  error. The old table object is not changed.
*/

bool reopen_table(Table *table)
{
  Table tmp;
  bool error= 1;
  Field **field;
  uint32_t key,part;
  TableList table_list;
  Session *session= table->in_use;

  assert(table->s->ref_count == 0);
  assert(!table->sort.io_cache);

#ifdef EXTRA_DEBUG
  if (table->db_stat)
    errmsg_printf(ERRMSG_LVL_ERROR, _("Table %s had a open data handler in reopen_table"),
		    table->alias);
#endif
  memset(&table_list, 0, sizeof(TableList));
  table_list.db=         table->s->db.str;
  table_list.table_name= table->s->table_name.str;
  table_list.table=      table;

  if (wait_for_locked_table_names(session, &table_list))
    return(1);                             // Thread was killed

  if (open_unireg_entry(session, &tmp, &table_list,
			table->alias,
                        table->s->table_cache_key.str,
                        table->s->table_cache_key.length))
    goto end;

  /* This list copies variables set by open_table */
  tmp.tablenr=		table->tablenr;
  tmp.used_fields=	table->used_fields;
  tmp.const_table=	table->const_table;
  tmp.null_row=		table->null_row;
  tmp.maybe_null=	table->maybe_null;
  tmp.status=		table->status;

  tmp.s->table_map_id=  table->s->table_map_id;

  /* Get state */
  tmp.in_use=    	session;
  tmp.reginfo.lock_type=table->reginfo.lock_type;

  /* Replace table in open list */
  tmp.next=		table->next;
  tmp.prev=		table->prev;

  if (table->file)
    table->closefrm(true);		// close file, free everything

  *table= tmp;
  table->default_column_bitmaps();
  table->file->change_table_ptr(table, table->s);

  assert(table->alias != 0);
  for (field=table->field ; *field ; field++)
  {
    (*field)->table= (*field)->orig_table= table;
    (*field)->table_name= &table->alias;
  }
  for (key=0 ; key < table->s->keys ; key++)
  {
    for (part=0 ; part < table->key_info[key].usable_key_parts ; part++)
      table->key_info[key].key_part[part].field->table= table;
  }
  /*
    Do not attach MERGE children here. The children might be reopened
    after the parent. Attach children after reopening all tables that
    require reopen. See for example reopen_tables().
  */

  broadcast_refresh();
  error=0;

 end:
  return(error);
}


/**
    Close all instances of a table open by this thread and replace
    them with exclusive name-locks.

    @param session        Thread context
    @param db         Database name for the table to be closed
    @param table_name Name of the table to be closed

    @note This function assumes that if we are not under LOCK TABLES,
          then there is only one table open and locked. This means that
          the function probably has to be adjusted before it can be used
          anywhere outside ALTER Table.

    @note Must not use TABLE_SHARE::table_name/db of the table being closed,
          the strings are used in a loop even after the share may be freed.
*/

void close_data_files_and_morph_locks(Session *session, const char *db,
                                      const char *table_name)
{
  Table *table;

  safe_mutex_assert_owner(&LOCK_open);

  if (session->lock)
  {
    /*
      If we are not under LOCK TABLES we should have only one table
      open and locked so it makes sense to remove the lock at once.
    */
    mysql_unlock_tables(session, session->lock);
    session->lock= 0;
  }

  /*
    Note that open table list may contain a name-lock placeholder
    for target table name if we process ALTER Table ... RENAME.
    So loop below makes sense even if we are not under LOCK TABLES.
  */
  for (table=session->open_tables; table ; table=table->next)
  {
    if (!strcmp(table->s->table_name.str, table_name) &&
	!strcmp(table->s->db.str, db))
    {
      if (session->locked_tables)
      {
        mysql_lock_remove(session, session->locked_tables, table, true);
      }
      table->open_placeholder= 1;
      close_handle_and_leave_table_as_lock(table);
    }
  }
  return;
}


/**
    Reopen all tables with closed data files.

    @param session         Thread context
    @param get_locks   Should we get locks after reopening tables ?
    @param mark_share_as_old  Mark share as old to protect from a impending
                              global read lock.

    @note Since this function can't properly handle prelocking and
          create placeholders it should be used in very special
          situations like FLUSH TABLES or ALTER Table. In general
          case one should just repeat open_tables()/lock_tables()
          combination when one needs tables to be reopened (for
          example see open_and_lock_tables()).

    @note One should have lock on LOCK_open when calling this.

    @return false in case of success, true - otherwise.
*/

bool reopen_tables(Session *session, bool get_locks, bool mark_share_as_old)
{
  Table *table,*next,**prev;
  Table **tables,**tables_ptr;			// For locks
  bool error=0, not_used;
  const uint32_t flags= DRIZZLE_LOCK_NOTIFY_IF_NEED_REOPEN |
                    DRIZZLE_LOCK_IGNORE_GLOBAL_READ_LOCK |
                    DRIZZLE_LOCK_IGNORE_FLUSH;

  if (!session->open_tables)
    return(0);

  safe_mutex_assert_owner(&LOCK_open);
  if (get_locks)
  {
    /*
      The ptr is checked later
      Do not handle locks of MERGE children.
    */
    uint32_t opens=0;
    for (table= session->open_tables; table ; table=table->next)
      opens++;
    tables= (Table**) malloc(sizeof(Table*)*opens);
  }
  else
    tables= &session->open_tables;
  tables_ptr =tables;

  prev= &session->open_tables;
  for (table=session->open_tables; table ; table=next)
  {
    uint32_t db_stat=table->db_stat;
    next=table->next;
    if (!tables || (!db_stat && reopen_table(table)))
    {
      my_error(ER_CANT_REOPEN_TABLE, MYF(0), table->alias);
      hash_delete(&open_cache,(unsigned char*) table);
      error=1;
    }
    else
    {
      *prev= table;
      prev= &table->next;
      /* Do not handle locks of MERGE children. */
      if (get_locks && !db_stat)
	*tables_ptr++= table;			// need new lock on this
      if (mark_share_as_old)
      {
	table->s->version=0;
	table->open_placeholder= 0;
      }
    }
  }
  *prev=0;
  if (tables != tables_ptr)			// Should we get back old locks
  {
    DRIZZLE_LOCK *lock;
    /*
      We should always get these locks. Anyway, we must not go into
      wait_for_tables() as it tries to acquire LOCK_open, which is
      already locked.
    */
    session->some_tables_deleted=0;
    if ((lock= mysql_lock_tables(session, tables, (uint32_t) (tables_ptr - tables),
                                 flags, &not_used)))
    {
      session->locked_tables=mysql_lock_merge(session->locked_tables,lock);
    }
    else
    {
      /*
        This case should only happen if there is a bug in the reopen logic.
        Need to issue error message to have a reply for the application.
        Not exactly what happened though, but close enough.
      */
      my_error(ER_LOCK_DEADLOCK, MYF(0));
      error=1;
    }
  }
  if (get_locks && tables)
  {
    free((unsigned char*) tables);
  }
  broadcast_refresh();
  return(error);
}


/**
    Close handlers for tables in list, but leave the Table structure
    intact so that we can re-open these quickly.

    @param session           Thread context
    @param table         Head of the list of Table objects
    @param morph_locks   true  - remove locks which we have on tables being closed
                                 but ensure that no DML or DDL will sneak in before
                                 we will re-open the table (i.e. temporarily morph
                                 our table-level locks into name-locks).
                         false - otherwise
    @param send_refresh  Should we awake waiters even if we didn't close any tables?
*/

static void close_old_data_files(Session *session, Table *table, bool morph_locks,
                                 bool send_refresh)
{
  bool found= send_refresh;

  for (; table ; table=table->next)
  {
    /*
      Reopen marked for flush.
    */
    if (table->needs_reopen_or_name_lock())
    {
      found=1;
      if (table->db_stat)
      {
	if (morph_locks)
	{
          Table *ulcktbl= table;
          if (ulcktbl->lock_count)
          {
            /*
              Wake up threads waiting for table-level lock on this table
              so they won't sneak in when we will temporarily remove our
              lock on it. This will also give them a chance to close their
              instances of this table.
            */
            mysql_lock_abort(session, ulcktbl, true);
            mysql_lock_remove(session, session->locked_tables, ulcktbl, true);
            ulcktbl->lock_count= 0;
          }
          if ((ulcktbl != table) && ulcktbl->db_stat)
          {
            /*
              Close the parent too. Note that parent can come later in
              the list of tables. It will then be noticed as closed and
              as a placeholder. When this happens, do not clear the
              placeholder flag. See the branch below ("***").
            */
            ulcktbl->open_placeholder= 1;
            close_handle_and_leave_table_as_lock(ulcktbl);
          }
          /*
            We want to protect the table from concurrent DDL operations
            (like RENAME Table) until we will re-open and re-lock it.
          */
	  table->open_placeholder= 1;
	}
        close_handle_and_leave_table_as_lock(table);
      }
      else if (table->open_placeholder && !morph_locks)
      {
        /*
          We come here only in close-for-back-off scenario. So we have to
          "close" create placeholder here to avoid deadlocks (for example,
          in case of concurrent execution of CREATE TABLE t1 SELECT * FROM t2
          and RENAME Table t2 TO t1). In close-for-re-open scenario we will
          probably want to let it stay.

          Note "***": We must not enter this branch if the placeholder
          flag has been set because of a former close through a child.
          See above the comment that refers to this note.
        */
        table->open_placeholder= 0;
      }
    }
  }
  if (found)
    broadcast_refresh();
  return;
}


/*
  Wait until all threads has closed the tables in the list
  We have also to wait if there is thread that has a lock on this table even
  if the table is closed
*/

bool table_is_used(Table *table, bool wait_for_name_lock)
{
  do
  {
    char *key= table->s->table_cache_key.str;
    uint32_t key_length= table->s->table_cache_key.length;

    HASH_SEARCH_STATE state;
    for (Table *search= (Table*) hash_first(&open_cache, (unsigned char*) key,
                                             key_length, &state);
	 search ;
         search= (Table*) hash_next(&open_cache, (unsigned char*) key,
                                    key_length, &state))
    {
      if (search->in_use == table->in_use)
        continue;                               // Name locked by this thread
      /*
        We can't use the table under any of the following conditions:
        - There is an name lock on it (Table is to be deleted or altered)
        - If we are in flush table and we didn't execute the flush
        - If the table engine is open and it's an old version
        (We must wait until all engines are shut down to use the table)
      */
      if ( (search->locked_by_name && wait_for_name_lock) ||
           (search->is_name_opened() && search->needs_reopen_or_name_lock()))
        return(1);
    }
  } while ((table=table->next));
  return(0);
}


/* Wait until all used tables are refreshed */

bool wait_for_tables(Session *session)
{
  bool result;

  session->set_proc_info("Waiting for tables");
  pthread_mutex_lock(&LOCK_open);
  while (!session->killed)
  {
    session->some_tables_deleted=0;
    close_old_data_files(session,session->open_tables,0,dropping_tables != 0);
    if (!table_is_used(session->open_tables,1))
      break;
    (void) pthread_cond_wait(&COND_refresh,&LOCK_open);
  }
  if (session->killed)
    result= 1;					// aborted
  else
  {
    /* Now we can open all tables without any interference */
    session->set_proc_info("Reopen tables");
    session->version= refresh_version;
    result=reopen_tables(session,0,0);
  }
  pthread_mutex_unlock(&LOCK_open);
  session->set_proc_info(0);
  return(result);
}


/*
  drop tables from locked list

  SYNOPSIS
    drop_locked_tables()
    session			Thread thandler
    db			Database
    table_name		Table name

  INFORMATION
    This is only called on drop tables

    The Table object for the dropped table is unlocked but still kept around
    as a name lock, which means that the table will be available for other
    thread as soon as we call unlock_table_names().
    If there is multiple copies of the table locked, all copies except
    the first, which acts as a name lock, is removed.

  RETURN
    #    If table existed, return table
    0	 Table was not locked
*/


Table *drop_locked_tables(Session *session,const char *db, const char *table_name)
{
  Table *table,*next,**prev, *found= 0;
  prev= &session->open_tables;

  /*
    Note that we need to hold LOCK_open while changing the
    open_tables list. Another thread may work on it.
    (See: remove_table_from_cache(), mysql_wait_completed_table())
    Closing a MERGE child before the parent would be fatal if the
    other thread tries to abort the MERGE lock in between.
  */
  for (table= session->open_tables; table ; table=next)
  {
    next=table->next;
    if (!strcmp(table->s->table_name.str, table_name) &&
	!strcmp(table->s->db.str, db))
    {
      mysql_lock_remove(session, session->locked_tables, table, true);

      if (!found)
      {
        found= table;
        /* Close engine table, but keep object around as a name lock */
        if (table->db_stat)
        {
          table->db_stat= 0;
          table->file->close();
        }
      }
      else
      {
        /* We already have a name lock, remove copy */
        hash_delete(&open_cache,(unsigned char*) table);
      }
    }
    else
    {
      *prev=table;
      prev= &table->next;
    }
  }
  *prev=0;
  if (found)
    broadcast_refresh();
  if (session->locked_tables && session->locked_tables->table_count == 0)
  {
    free((unsigned char*) session->locked_tables);
    session->locked_tables=0;
  }
  return(found);
}


/*
  If we have the table open, which only happens when a LOCK Table has been
  done on the table, change the lock type to a lock that will abort all
  other threads trying to get the lock.
*/

void abort_locked_tables(Session *session,const char *db, const char *table_name)
{
  Table *table;
  for (table= session->open_tables; table ; table= table->next)
  {
    if (!strcmp(table->s->table_name.str, table_name) &&
	!strcmp(table->s->db.str, db))
    {
      /* If MERGE child, forward lock handling to parent. */
      mysql_lock_abort(session, table, true);
      break;
    }
  }
}


/*
  Function to assign a new table map id to a table share.

  PARAMETERS

    share - Pointer to table share structure

  DESCRIPTION

    We are intentionally not checking that share->mutex is locked
    since this function should only be called when opening a table
    share and before it is entered into the table_def_cache (meaning
    that it cannot be fetched by another thread, even accidentally).

  PRE-CONDITION(S)

    share is non-NULL
    The LOCK_open mutex is locked

  POST-CONDITION(S)

    share->table_map_id is given a value that with a high certainty is
    not used by any other table (the only case where a table id can be
    reused is on wrap-around, which means more than 4 billion table
    share opens have been executed while one table was open all the
    time).

    share->table_map_id is not UINT32_MAX.
 */
void assign_new_table_id(TABLE_SHARE *share)
{
  static uint32_t last_table_id= UINT32_MAX;

  /* Preconditions */
  assert(share != NULL);
  safe_mutex_assert_owner(&LOCK_open);

  ulong tid= ++last_table_id;                   /* get next id */
  /*
    There is one reserved number that cannot be used.  Remember to
    change this when 6-byte global table id's are introduced.
  */
  if (unlikely(tid == UINT32_MAX))
    tid= ++last_table_id;
  share->table_map_id= tid;

  /* Post conditions */
  assert(share->table_map_id != UINT32_MAX);

  return;
}

/*
  Load a table definition from file and open unireg table

  SYNOPSIS
    open_unireg_entry()
    session			Thread handle
    entry		Store open table definition here
    table_list		TableList with db, table_name
    alias		Alias name
    cache_key		Key for share_cache
    cache_key_length	length of cache_key

  NOTES
   Extra argument for open is taken from session->open_options
   One must have a lock on LOCK_open when calling this function

  RETURN
    0	ok
    #	Error
*/

static int open_unireg_entry(Session *session, Table *entry, TableList *table_list,
                             const char *alias,
                             char *cache_key, uint32_t cache_key_length)
{
  int error;
  TABLE_SHARE *share;
  uint32_t discover_retry_count= 0;

  safe_mutex_assert_owner(&LOCK_open);
retry:
  if (!(share= get_table_share_with_create(session, table_list, cache_key,
                                           cache_key_length,
                                           table_list->i_s_requested_object,
                                           &error)))
    return(1);

  while ((error= open_table_from_share(session, share, alias,
                                       (uint32_t) (HA_OPEN_KEYFILE |
                                               HA_OPEN_RNDFILE |
                                               HA_GET_INDEX |
                                               HA_TRY_READ_ONLY),
                                       (EXTRA_RECORD),
                                       session->open_options, entry, OTM_OPEN)))
  {
    if (error == 7)                             // Table def changed
    {
      share->version= 0;                        // Mark share as old
      if (discover_retry_count++)               // Retry once
        goto err;

      /*
        TODO:
        Here we should wait until all threads has released the table.
        For now we do one retry. This may cause a deadlock if there
        is other threads waiting for other tables used by this thread.

        Proper fix would be to if the second retry failed:
        - Mark that table def changed
        - Return from open table
        - Close all tables used by this thread
        - Start waiting that the share is released
        - Retry by opening all tables again
      */

      /*
        TO BE FIXED
        To avoid deadlock, only wait for release if no one else is
        using the share.
      */
      if (share->ref_count != 1)
        goto err;
      /* Free share and wait until it's released by all threads */
      release_table_share(share, RELEASE_WAIT_FOR_DROP);
      if (!session->killed)
      {
        drizzle_reset_errors(session, 1);         // Clear warnings
        session->clear_error();                 // Clear error message
        goto retry;
      }
      return(1);
    }
    if (!entry->s || !entry->s->crashed)
      goto err;
     // Code below is for repairing a crashed file
     if ((error= lock_table_name(session, table_list, true)))
     {
       if (error < 0)
 	goto err;
       if (wait_for_locked_table_names(session, table_list))
       {
 	unlock_table_name(session, table_list);
 	goto err;
       }
     }
     pthread_mutex_unlock(&LOCK_open);
     session->clear_error();				// Clear error message
     error= 0;
     if (open_table_from_share(session, share, alias,
                               (uint32_t) (HA_OPEN_KEYFILE | HA_OPEN_RNDFILE |
                                       HA_GET_INDEX |
                                       HA_TRY_READ_ONLY),
                               EXTRA_RECORD,
                               ha_open_options | HA_OPEN_FOR_REPAIR,
                               entry, OTM_OPEN) || ! entry->file ||
        (entry->file->is_crashed() && entry->file->ha_check_and_repair(session)))
     {
       /* Give right error message */
       session->clear_error();
       my_error(ER_NOT_KEYFILE, MYF(0), share->table_name.str, my_errno);
       errmsg_printf(ERRMSG_LVL_ERROR, _("Couldn't repair table: %s.%s"), share->db.str,
                       share->table_name.str);
       if (entry->file)
 	entry->closefrm(false);
       error=1;
     }
     else
       session->clear_error();			// Clear error message
     pthread_mutex_lock(&LOCK_open);
     unlock_table_name(session, table_list);

     if (error)
       goto err;
     break;
   }

  /*
    If we are here, there was no fatal error (but error may be still
    unitialized).
  */
  if (unlikely(entry->file->implicit_emptied))
  {
    entry->file->implicit_emptied= 0;
    {
      char *query, *end;
      uint32_t query_buf_size= 20 + share->db.length + share->table_name.length +1;
      if ((query= (char*) malloc(query_buf_size)))
      {
        /* 
          "this DELETE FROM is needed even with row-based binlogging"

          We inherited this from MySQL. TODO: fix it to issue a propper truncate
          of the table (though that may not be completely right sematics).
        */
        end= query;
        end+= sprintf(query, "DELETE FROM `%s`.`%s`", share->db.str,
                      share->table_name.str);
        (void)replicator_statement(session, query, (size_t)(end - query));
        free(query);
      }
      else
      {
        errmsg_printf(ERRMSG_LVL_ERROR, _("When opening HEAP table, could not allocate memory "
                                          "to write 'DELETE FROM `%s`.`%s`' to replication"),
                      table_list->db, table_list->table_name);
        my_error(ER_OUTOFMEMORY, MYF(0), query_buf_size);
        entry->closefrm(false);
        goto err;
      }
    }
  }
  return(0);

err:
  release_table_share(share, RELEASE_NORMAL);
  return(1);
}


/*
  Open all tables in list

  SYNOPSIS
    open_tables()
    session - thread handler
    start - list of tables in/out
    counter - number of opened tables will be return using this parameter
    flags   - bitmap of flags to modify how the tables will be open:
              DRIZZLE_LOCK_IGNORE_FLUSH - open table even if someone has
              done a flush or namelock on it.

  NOTE
    Unless we are already in prelocked mode, this function will also precache
    all SP/SFs explicitly or implicitly (via views and triggers) used by the
    query and add tables needed for their execution to table list. If resulting
    tables list will be non empty it will mark query as requiring precaching.
    Prelocked mode will be enabled for such query during lock_tables() call.

    If query for which we are opening tables is already marked as requiring
    prelocking it won't do such precaching and will simply reuse table list
    which is already built.

  RETURN
    0  - OK
    -1 - error
*/

int open_tables(Session *session, TableList **start, uint32_t *counter, uint32_t flags)
{
  TableList *tables= NULL;
  bool refresh;
  int result=0;
  MEM_ROOT new_frm_mem;
  /* Also used for indicating that prelocking is need */
  bool safe_to_ignore_table;

  /*
    temporary mem_root for new .frm parsing.
    TODO: variables for size
  */
  init_sql_alloc(&new_frm_mem, 8024, 8024);

  session->current_tablenr= 0;
 restart:
  *counter= 0;
  session->set_proc_info("Opening tables");

  /*
    For every table in the list of tables to open, try to find or open
    a table.
  */
  for (tables= *start; tables ;tables= tables->next_global)
  {
    safe_to_ignore_table= false;

    /*
      Ignore placeholders for derived tables. After derived tables
      processing, link to created temporary table will be put here.
      If this is derived table for view then we still want to process
      routines used by this view.
     */
    if (tables->derived)
    {
      continue;
    }
    /*
      If this TableList object is a placeholder for an information_schema
      table, create a temporary table to represent the information_schema
      table in the query. Do not fill it yet - will be filled during
      execution.
    */
    if (tables->schema_table)
    {
      if (!mysql_schema_table(session, session->lex, tables))
        continue;
      return(-1);
    }
    (*counter)++;

    /*
      Not a placeholder: must be a base table or a view, and the table is
      not opened yet. Try to open the table.
    */
    if (!tables->table)
      tables->table= open_table(session, tables, &refresh, flags);

    if (!tables->table)
    {
      free_root(&new_frm_mem, MYF(MY_KEEP_PREALLOC));

      if (refresh)				// Refresh in progress
      {
        /*
          We have met name-locked or old version of table. Now we have
          to close all tables which are not up to date. We also have to
          throw away set of prelocked tables (and thus close tables from
          this set that were open by now) since it possible that one of
          tables which determined its content was changed.

          Instead of implementing complex/non-robust logic mentioned
          above we simply close and then reopen all tables.

          In order to prepare for recalculation of set of prelocked tables
          we pretend that we have finished calculation which we were doing
          currently.
        */
        close_tables_for_reopen(session, start);
	goto restart;
      }

      if (safe_to_ignore_table)
        continue;

      result= -1;				// Fatal error
      break;
    }
    if (tables->lock_type != TL_UNLOCK && ! session->locked_tables)
    {
      if (tables->lock_type == TL_WRITE_DEFAULT)
        tables->table->reginfo.lock_type= session->update_lock_default;
      else if (tables->table->s->tmp_table == NO_TMP_TABLE)
        tables->table->reginfo.lock_type= tables->lock_type;
    }
  }

  session->set_proc_info(0);
  free_root(&new_frm_mem, MYF(0));              // Free pre-alloced block

  if (result && tables)
  {
    /*
      Some functions determine success as (tables->table != NULL).
      tables->table is in session->open_tables.
    */
    tables->table= NULL;
  }
  return(result);
}


/*
  Check that lock is ok for tables; Call start stmt if ok

  SYNOPSIS
    check_lock_and_start_stmt()
    session			Thread handle
    table_list		Table to check
    lock_type		Lock used for table

  RETURN VALUES
  0	ok
  1	error
*/

static bool check_lock_and_start_stmt(Session *session, Table *table,
				      thr_lock_type lock_type)
{
  int error;

  if ((int) lock_type >= (int) TL_WRITE_ALLOW_READ &&
      (int) table->reginfo.lock_type < (int) TL_WRITE_ALLOW_READ)
  {
    my_error(ER_TABLE_NOT_LOCKED_FOR_WRITE, MYF(0),table->alias);
    return(1);
  }
  if ((error=table->file->start_stmt(session, lock_type)))
  {
    table->file->print_error(error,MYF(0));
    return(1);
  }
  return(0);
}


/**
  @brief Open and lock one table

  @param[in]    session             thread handle
  @param[in]    table_l         table to open is first table in this list
  @param[in]    lock_type       lock to use for table

  @return       table
    @retval     != NULL         OK, opened table returned
    @retval     NULL            Error

  @note
    If ok, the following are also set:
      table_list->lock_type 	lock_type
      table_list->table		table

  @note
    If table_l is a list, not a single table, the list is temporarily
    broken.

  @detail
    This function is meant as a replacement for open_ltable() when
    MERGE tables can be opened. open_ltable() cannot open MERGE tables.

    There may be more differences between open_n_lock_single_table() and
    open_ltable(). One known difference is that open_ltable() does
    neither call decide_logging_format() nor handle some other logging
    and locking issues because it does not call lock_tables().
*/

Table *open_n_lock_single_table(Session *session, TableList *table_l,
                                thr_lock_type lock_type)
{
  TableList *save_next_global;

  /* Remember old 'next' pointer. */
  save_next_global= table_l->next_global;
  /* Break list. */
  table_l->next_global= NULL;

  /* Set requested lock type. */
  table_l->lock_type= lock_type;

  /* Open the table. */
  if (simple_open_n_lock_tables(session, table_l))
    table_l->table= NULL; /* Just to be sure. */

  /* Restore list. */
  table_l->next_global= save_next_global;

  return(table_l->table);
}


/*
  Open and lock one table

  SYNOPSIS
    open_ltable()
    session			Thread handler
    table_list		Table to open is first table in this list
    lock_type		Lock to use for open
    lock_flags          Flags passed to mysql_lock_table

  NOTE
    This function don't do anything like SP/SF/views/triggers analysis done
    in open_tables(). It is intended for opening of only one concrete table.
    And used only in special contexts.

  RETURN VALUES
    table		Opened table
    0			Error

    If ok, the following are also set:
      table_list->lock_type 	lock_type
      table_list->table		table
*/

Table *open_ltable(Session *session, TableList *table_list, thr_lock_type lock_type,
                   uint32_t lock_flags)
{
  Table *table;
  bool refresh;

  session->set_proc_info("Opening table");
  session->current_tablenr= 0;
  while (!(table= open_table(session, table_list, &refresh, 0)) &&
         refresh)
    ;

  if (table)
  {
    table_list->lock_type= lock_type;
    table_list->table=	   table;
    if (session->locked_tables)
    {
      if (check_lock_and_start_stmt(session, table, lock_type))
	table= 0;
    }
    else
    {
      assert(session->lock == 0);	// You must lock everything at once
      if ((table->reginfo.lock_type= lock_type) != TL_UNLOCK)
	if (! (session->lock= mysql_lock_tables(session, &table_list->table, 1,
                                            lock_flags, &refresh)))
	  table= 0;
    }
  }

  session->set_proc_info(0);
  return(table);
}


/*
  Open all tables in list, locks them and optionally process derived tables.

  SYNOPSIS
    open_and_lock_tables_derived()
    session		- thread handler
    tables	- list of tables for open&locking
    derived     - if to handle derived tables

  RETURN
    false - ok
    true  - error

  NOTE
    The lock will automaticaly be freed by close_thread_tables()

  NOTE
    There are two convenience functions:
    - simple_open_n_lock_tables(session, tables)  without derived handling
    - open_and_lock_tables(session, tables)       with derived handling
    Both inline functions call open_and_lock_tables_derived() with
    the third argument set appropriately.
*/

int open_and_lock_tables_derived(Session *session, TableList *tables, bool derived)
{
  uint32_t counter;
  bool need_reopen;

  for ( ; ; )
  {
    if (open_tables(session, &tables, &counter, 0))
      return(-1);

    if (!lock_tables(session, tables, counter, &need_reopen))
      break;
    if (!need_reopen)
      return(-1);
    close_tables_for_reopen(session, &tables);
  }
  if (derived &&
      (mysql_handle_derived(session->lex, &mysql_derived_prepare) ||
       (session->fill_derived_tables() &&
        mysql_handle_derived(session->lex, &mysql_derived_filling))))
    return(true); /* purecov: inspected */
  return(0);
}


/*
  Open all tables in list and process derived tables

  SYNOPSIS
    open_normal_and_derived_tables
    session		- thread handler
    tables	- list of tables for open
    flags       - bitmap of flags to modify how the tables will be open:
                  DRIZZLE_LOCK_IGNORE_FLUSH - open table even if someone has
                  done a flush or namelock on it.

  RETURN
    false - ok
    true  - error

  NOTE
    This is to be used on prepare stage when you don't read any
    data from the tables.
*/

bool open_normal_and_derived_tables(Session *session, TableList *tables, uint32_t flags)
{
  uint32_t counter;
  assert(!session->fill_derived_tables());
  if (open_tables(session, &tables, &counter, flags) ||
      mysql_handle_derived(session->lex, &mysql_derived_prepare))
    return(true); /* purecov: inspected */
  return(0);
}

/*
  Lock all tables in list

  SYNOPSIS
    lock_tables()
    session			Thread handler
    tables		Tables to lock
    count		Number of opened tables
    need_reopen         Out parameter which if true indicates that some
                        tables were dropped or altered during this call
                        and therefore invoker should reopen tables and
                        try to lock them once again (in this case
                        lock_tables() will also return error).

  NOTES
    You can't call lock_tables twice, as this would break the dead-lock-free
    handling thr_lock gives us.  You most always get all needed locks at
    once.

    If query for which we are calling this function marked as requring
    prelocking, this function will do implicit LOCK TABLES and change
    session::prelocked_mode accordingly.

  RETURN VALUES
   0	ok
   -1	Error
*/

int lock_tables(Session *session, TableList *tables, uint32_t count, bool *need_reopen)
{
  TableList *table;

  /*
    We can't meet statement requiring prelocking if we already
    in prelocked mode.
  */
  *need_reopen= false;

  if (!tables)
    return 0;

  if (!session->locked_tables)
  {
    assert(session->lock == 0);	// You must lock everything at once
    Table **start,**ptr;
    uint32_t lock_flag= DRIZZLE_LOCK_NOTIFY_IF_NEED_REOPEN;

    if (!(ptr=start=(Table**) session->alloc(sizeof(Table*)*count)))
      return(-1);
    for (table= tables; table; table= table->next_global)
    {
      if (!table->placeholder())
	*(ptr++)= table->table;
    }

    if (!(session->lock= mysql_lock_tables(session, start, (uint32_t) (ptr - start),
                                       lock_flag, need_reopen)))
    {
      return(-1);
    }
  }
  else
  {
    TableList *first_not_own= session->lex->first_not_own_table();
    /*
      When open_and_lock_tables() is called for a single table out of
      a table list, the 'next_global' chain is temporarily broken. We
      may not find 'first_not_own' before the end of the "list".
      Look for example at those places where open_n_lock_single_table()
      is called. That function implements the temporary breaking of
      a table list for opening a single table.
    */
    for (table= tables;
         table && table != first_not_own;
         table= table->next_global)
    {
      if (!table->placeholder() &&
	  check_lock_and_start_stmt(session, table->table, table->lock_type))
      {
	return(-1);
      }
    }
  }

  return 0;
}


/*
  Prepare statement for reopening of tables and recalculation of set of
  prelocked tables.

  SYNOPSIS
    close_tables_for_reopen()
      session    in     Thread context
      tables in/out List of tables which we were trying to open and lock

*/

void close_tables_for_reopen(Session *session, TableList **tables)
{
  /*
    If table list consists only from tables from prelocking set, table list
    for new attempt should be empty, so we have to update list's root pointer.
  */
  if (session->lex->first_not_own_table() == *tables)
    *tables= 0;
  session->lex->chop_off_not_own_tables();
  for (TableList *tmp= *tables; tmp; tmp= tmp->next_global)
    tmp->table= 0;
  close_thread_tables(session);
}


/*
  Open a single table without table caching and don't set it in open_list

  SYNPOSIS
    open_temporary_table()
    session		  Thread object
    path	  Path (without .frm)
    db		  database
    table_name	  Table name
    link_in_list  1 if table should be linked into session->temporary_tables

 NOTES:
    Used by alter_table to open a temporary table and when creating
    a temporary table with CREATE TEMPORARY ...

 RETURN
   0  Error
   #  Table object
*/

Table *open_temporary_table(Session *session, const char *path, const char *db,
			    const char *table_name, bool link_in_list,
                            open_table_mode open_mode)
{
  Table *tmp_table;
  TABLE_SHARE *share;
  char cache_key[MAX_DBKEY_LENGTH], *saved_cache_key, *tmp_path;
  uint32_t key_length, path_length;
  TableList table_list;

  table_list.db=         (char*) db;
  table_list.table_name= (char*) table_name;
  /* Create the cache_key for temporary tables */
  key_length= create_table_def_key(session, cache_key, &table_list, 1);
  path_length= strlen(path);

  if (!(tmp_table= (Table*) malloc(sizeof(*tmp_table) + sizeof(*share) +
                                   path_length + 1 + key_length)))
    return NULL;

  share= (TABLE_SHARE*) (tmp_table+1);
  tmp_path= (char*) (share+1);
  saved_cache_key= strcpy(tmp_path, path)+path_length+1;
  memcpy(saved_cache_key, cache_key, key_length);

  init_tmp_table_share(session, share, saved_cache_key, key_length,
                       strchr(saved_cache_key, '\0')+1, tmp_path);

  if (open_table_def(session, share, 0) ||
      open_table_from_share(session, share, table_name,
                            (open_mode == OTM_ALTER) ? 0 :
                            (uint32_t) (HA_OPEN_KEYFILE | HA_OPEN_RNDFILE |
                                    HA_GET_INDEX),
                            (open_mode == OTM_ALTER) ?
                              (EXTRA_RECORD | OPEN_FRM_FILE_ONLY)
                            : (EXTRA_RECORD),
                            ha_open_options,
                            tmp_table, open_mode))
  {
    /* No need to lock share->mutex as this is not needed for tmp tables */
    free_table_share(share);
    free((char*) tmp_table);
    return(0);
  }

  tmp_table->reginfo.lock_type= TL_WRITE;	 // Simulate locked
  if (open_mode == OTM_ALTER)
  {
    /*
       Temporary table has been created with frm_only
       and has not been created in any storage engine
    */
    share->tmp_table= TMP_TABLE_FRM_FILE_ONLY;
  }
  else
    share->tmp_table= (tmp_table->file->has_transactions() ?
                       TRANSACTIONAL_TMP_TABLE : NON_TRANSACTIONAL_TMP_TABLE);

  if (link_in_list)
  {
    /* growing temp list at the head */
    tmp_table->next= session->temporary_tables;
    if (tmp_table->next)
      tmp_table->next->prev= tmp_table;
    session->temporary_tables= tmp_table;
    session->temporary_tables->prev= 0;
  }
  tmp_table->pos_in_table_list= 0;
  return(tmp_table);
}


bool rm_temporary_table(handlerton *base, char *path)
{
  bool error=0;
  handler *file;

  if(delete_table_proto_file(path))
    error=1; /* purecov: inspected */

  file= get_new_handler((TABLE_SHARE*) 0, current_session->mem_root, base);
  if (file && file->ha_delete_table(path))
  {
    error=1;
    errmsg_printf(ERRMSG_LVL_WARN, _("Could not remove temporary table: '%s', error: %d"),
                      path, my_errno);
  }
  delete file;
  return(error);
}


/*****************************************************************************
* The following find_field_in_XXX procedures implement the core of the
* name resolution functionality. The entry point to resolve a column name in a
* list of tables is 'find_field_in_tables'. It calls 'find_field_in_table_ref'
* for each table reference. In turn, depending on the type of table reference,
* 'find_field_in_table_ref' calls one of the 'find_field_in_XXX' procedures
* below specific for the type of table reference.
******************************************************************************/

/* Special Field pointers as return values of find_field_in_XXX functions. */
Field *not_found_field= (Field*) 0x1;
Field *view_ref_found= (Field*) 0x2;

#define WRONG_GRANT (Field*) -1

static void update_field_dependencies(Session *session, Field *field, Table *table)
{
  if (session->mark_used_columns != MARK_COLUMNS_NONE)
  {
    MY_BITMAP *current_bitmap, *other_bitmap;

    /*
      We always want to register the used keys, as the column bitmap may have
      been set for all fields (for example for view).
    */

    table->covering_keys.intersect(field->part_of_key);
    table->merge_keys.merge(field->part_of_key);

    if (session->mark_used_columns == MARK_COLUMNS_READ)
    {
      current_bitmap= table->read_set;
      other_bitmap=   table->write_set;
    }
    else
    {
      current_bitmap= table->write_set;
      other_bitmap=   table->read_set;
    }

    if (bitmap_fast_test_and_set(current_bitmap, field->field_index))
    {
      if (session->mark_used_columns == MARK_COLUMNS_WRITE)
        session->dup_field= field;
      return;
    }
    if (table->get_fields_in_item_tree)
      field->flags|= GET_FIXED_FIELDS_FLAG;
    table->used_fields++;
  }
  else if (table->get_fields_in_item_tree)
    field->flags|= GET_FIXED_FIELDS_FLAG;
  return;
}


/*
  Find field by name in a NATURAL/USING join table reference.

  SYNOPSIS
    find_field_in_natural_join()
    session			 [in]  thread handler
    table_ref            [in]  table reference to search
    name		 [in]  name of field
    length		 [in]  length of name
    ref                  [in/out] if 'name' is resolved to a view field, ref is
                               set to point to the found view field
    register_tree_change [in]  true if ref is not stack variable and we
                               need register changes in item tree
    actual_table         [out] the original table reference where the field
                               belongs - differs from 'table_list' only for
                               NATURAL/USING joins

  DESCRIPTION
    Search for a field among the result fields of a NATURAL/USING join.
    Notice that this procedure is called only for non-qualified field
    names. In the case of qualified fields, we search directly the base
    tables of a natural join.

  RETURN
    NULL        if the field was not found
    WRONG_GRANT if no access rights to the found field
    #           Pointer to the found Field
*/

static Field *
find_field_in_natural_join(Session *session, TableList *table_ref,
                           const char *name, uint32_t , Item **,
                           bool, TableList **actual_table)
{
  List_iterator_fast<Natural_join_column>
    field_it(*(table_ref->join_columns));
  Natural_join_column *nj_col, *curr_nj_col;
  Field *found_field;

  assert(table_ref->is_natural_join && table_ref->join_columns);
  assert(*actual_table == NULL);

  for (nj_col= NULL, curr_nj_col= field_it++; curr_nj_col;
       curr_nj_col= field_it++)
  {
    if (!my_strcasecmp(system_charset_info, curr_nj_col->name(), name))
    {
      if (nj_col)
      {
        my_error(ER_NON_UNIQ_ERROR, MYF(0), name, session->where);
        return(NULL);
      }
      nj_col= curr_nj_col;
    }
  }
  if (!nj_col)
    return(NULL);
  {
    /* This is a base table. */
    assert(nj_col->table_ref->table == nj_col->table_field->table);
    found_field= nj_col->table_field;
    update_field_dependencies(session, found_field, nj_col->table_ref->table);
  }

  *actual_table= nj_col->table_ref;

  return(found_field);
}


/*
  Find field by name in a base table or a view with temp table algorithm.

  SYNOPSIS
    find_field_in_table()
    session				thread handler
    table			table where to search for the field
    name			name of field
    length			length of name
    allow_rowid			do allow finding of "_rowid" field?
    cached_field_index_ptr	cached position in field list (used to speedup
                                lookup for fields in prepared tables)

  RETURN
    0	field is not found
    #	pointer to field
*/

Field *
find_field_in_table(Session *session, Table *table, const char *name, uint32_t length,
                    bool allow_rowid, uint32_t *cached_field_index_ptr)
{
  Field **field_ptr, *field;
  uint32_t cached_field_index= *cached_field_index_ptr;

  /* We assume here that table->field < NO_CACHED_FIELD_INDEX = UINT_MAX */
  if (cached_field_index < table->s->fields &&
      !my_strcasecmp(system_charset_info,
                     table->field[cached_field_index]->field_name, name))
    field_ptr= table->field + cached_field_index;
  else if (table->s->name_hash.records)
  {
    field_ptr= (Field**) hash_search(&table->s->name_hash, (unsigned char*) name,
                                     length);
    if (field_ptr)
    {
      /*
        field_ptr points to field in TABLE_SHARE. Convert it to the matching
        field in table
      */
      field_ptr= (table->field + (field_ptr - table->s->field));
    }
  }
  else
  {
    if (!(field_ptr= table->field))
      return((Field *)0);
    for (; *field_ptr; ++field_ptr)
      if (!my_strcasecmp(system_charset_info, (*field_ptr)->field_name, name))
        break;
  }

  if (field_ptr && *field_ptr)
  {
    if ((*field_ptr)->vcol_info)
    {
      if (session->mark_used_columns != MARK_COLUMNS_NONE)
      {
        Item *vcol_item= (*field_ptr)->vcol_info->expr_item;
        assert(vcol_item);
        vcol_item->walk(&Item::register_field_in_read_map, 1, (unsigned char *) 0);
        /*
          Set the virtual field for write here if
          1) this procedure is called for a read-only operation (SELECT), and
          2) the virtual column is not phycically stored in the table
        */
        if ((session->mark_used_columns != MARK_COLUMNS_WRITE) &&
            (not (*field_ptr)->is_stored))
          bitmap_set_bit((*field_ptr)->table->write_set, (*field_ptr)->field_index);
      }
    }
    *cached_field_index_ptr= field_ptr - table->field;
    field= *field_ptr;
  }
  else
  {
    if (!allow_rowid ||
        my_strcasecmp(system_charset_info, name, "_rowid") ||
        table->s->rowid_field_offset == 0)
      return((Field*) 0);
    field= table->field[table->s->rowid_field_offset-1];
  }

  update_field_dependencies(session, field, table);

  return(field);
}


/*
  Find field in a table reference.

  SYNOPSIS
    find_field_in_table_ref()
    session			   [in]  thread handler
    table_list		   [in]  table reference to search
    name		   [in]  name of field
    length		   [in]  field length of name
    item_name              [in]  name of item if it will be created (VIEW)
    db_name                [in]  optional database name that qualifies the
    table_name             [in]  optional table name that qualifies the field
    ref		       [in/out] if 'name' is resolved to a view field, ref
                                 is set to point to the found view field
    check_privileges       [in]  check privileges
    allow_rowid		   [in]  do allow finding of "_rowid" field?
    cached_field_index_ptr [in]  cached position in field list (used to
                                 speedup lookup for fields in prepared tables)
    register_tree_change   [in]  true if ref is not stack variable and we
                                 need register changes in item tree
    actual_table           [out] the original table reference where the field
                                 belongs - differs from 'table_list' only for
                                 NATURAL_USING joins.

  DESCRIPTION
    Find a field in a table reference depending on the type of table
    reference. There are three types of table references with respect
    to the representation of their result columns:
    - an array of Field_translator objects for MERGE views and some
      information_schema tables,
    - an array of Field objects (and possibly a name hash) for stored
      tables,
    - a list of Natural_join_column objects for NATURAL/USING joins.
    This procedure detects the type of the table reference 'table_list'
    and calls the corresponding search routine.

  RETURN
    0			field is not found
    view_ref_found	found value in VIEW (real result is in *ref)
    #			pointer to field
*/

Field *
find_field_in_table_ref(Session *session, TableList *table_list,
                        const char *name, uint32_t length,
                        const char *item_name, const char *db_name,
                        const char *table_name, Item **ref,
                        bool check_privileges, bool allow_rowid,
                        uint32_t *cached_field_index_ptr,
                        bool register_tree_change, TableList **actual_table)
{
  Field *fld= NULL;

  assert(table_list->alias);
  assert(name);
  assert(item_name);

  /*
    Check that the table and database that qualify the current field name
    are the same as the table reference we are going to search for the field.

    Exclude from the test below nested joins because the columns in a
    nested join generally originate from different tables. Nested joins
    also have no table name, except when a nested join is a merge view
    or an information schema table.

    We include explicitly table references with a 'field_translation' table,
    because if there are views over natural joins we don't want to search
    inside the view, but we want to search directly in the view columns
    which are represented as a 'field_translation'.

    TODO: Ensure that table_name, db_name and tables->db always points to
          something !
  */
  if (/* Exclude nested joins. */
      (!table_list->nested_join) &&
       /* Include merge views and information schema tables. */
      /*
        Test if the field qualifiers match the table reference we plan
        to search.
      */
      table_name && table_name[0] &&
      (my_strcasecmp(table_alias_charset, table_list->alias, table_name) ||
       (db_name && db_name[0] && table_list->db && table_list->db[0] &&
        strcmp(db_name, table_list->db))))
    return(0);

  *actual_table= NULL;

  if (!table_list->nested_join)
  {
    /* 'table_list' is a stored table. */
    assert(table_list->table);
    if ((fld= find_field_in_table(session, table_list->table, name, length,
                                  allow_rowid,
                                  cached_field_index_ptr)))
      *actual_table= table_list;
  }
  else
  {
    /*
      'table_list' is a NATURAL/USING join, or an operand of such join that
      is a nested join itself.

      If the field name we search for is qualified, then search for the field
      in the table references used by NATURAL/USING the join.
    */
    if (table_name && table_name[0])
    {
      List_iterator<TableList> it(table_list->nested_join->join_list);
      TableList *table;
      while ((table= it++))
      {
        if ((fld= find_field_in_table_ref(session, table, name, length, item_name,
                                          db_name, table_name, ref,
                                          check_privileges, allow_rowid,
                                          cached_field_index_ptr,
                                          register_tree_change, actual_table)))
          return(fld);
      }
      return(0);
    }
    /*
      Non-qualified field, search directly in the result columns of the
      natural join. The condition of the outer IF is true for the top-most
      natural join, thus if the field is not qualified, we will search
      directly the top-most NATURAL/USING join.
    */
    fld= find_field_in_natural_join(session, table_list, name, length, ref,
                                    register_tree_change, actual_table);
  }

  if (fld)
  {
      if (session->mark_used_columns != MARK_COLUMNS_NONE)
      {
        /*
          Get rw_set correct for this field so that the handler
          knows that this field is involved in the query and gets
          retrieved/updated
         */
        Field *field_to_set= NULL;
        if (fld == view_ref_found)
        {
          Item *it= (*ref)->real_item();
          if (it->type() == Item::FIELD_ITEM)
            field_to_set= ((Item_field*)it)->field;
          else
          {
            if (session->mark_used_columns == MARK_COLUMNS_READ)
              it->walk(&Item::register_field_in_read_map, 1, (unsigned char *) 0);
          }
        }
        else
          field_to_set= fld;
        if (field_to_set)
        {
          Table *table= field_to_set->table;
          if (session->mark_used_columns == MARK_COLUMNS_READ)
            bitmap_set_bit(table->read_set, field_to_set->field_index);
          else
            bitmap_set_bit(table->write_set, field_to_set->field_index);
        }
      }
  }
  return(fld);
}


/*
  Find field in table, no side effects, only purpose is to check for field
  in table object and get reference to the field if found.

  SYNOPSIS
  find_field_in_table_sef()

  table                         table where to find
  name                          Name of field searched for

  RETURN
    0                   field is not found
    #                   pointer to field
*/

Field *find_field_in_table_sef(Table *table, const char *name)
{
  Field **field_ptr;
  if (table->s->name_hash.records)
  {
    field_ptr= (Field**)hash_search(&table->s->name_hash,(unsigned char*) name,
                                    strlen(name));
    if (field_ptr)
    {
      /*
        field_ptr points to field in TABLE_SHARE. Convert it to the matching
        field in table
      */
      field_ptr= (table->field + (field_ptr - table->s->field));
    }
  }
  else
  {
    if (!(field_ptr= table->field))
      return (Field *)0;
    for (; *field_ptr; ++field_ptr)
      if (!my_strcasecmp(system_charset_info, (*field_ptr)->field_name, name))
        break;
  }
  if (field_ptr)
    return *field_ptr;
  else
    return (Field *)0;
}


/*
  Find field in table list.

  SYNOPSIS
    find_field_in_tables()
    session			  pointer to current thread structure
    item		  field item that should be found
    first_table           list of tables to be searched for item
    last_table            end of the list of tables to search for item. If NULL
                          then search to the end of the list 'first_table'.
    ref			  if 'item' is resolved to a view field, ref is set to
                          point to the found view field
    report_error	  Degree of error reporting:
                          - IGNORE_ERRORS then do not report any error
                          - IGNORE_EXCEPT_NON_UNIQUE report only non-unique
                            fields, suppress all other errors
                          - REPORT_EXCEPT_NON_UNIQUE report all other errors
                            except when non-unique fields were found
                          - REPORT_ALL_ERRORS
    check_privileges      need to check privileges
    register_tree_change  true if ref is not a stack variable and we
                          to need register changes in item tree

  RETURN VALUES
    0			If error: the found field is not unique, or there are
                        no sufficient access priviliges for the found field,
                        or the field is qualified with non-existing table.
    not_found_field	The function was called with report_error ==
                        (IGNORE_ERRORS || IGNORE_EXCEPT_NON_UNIQUE) and a
			field was not found.
    view_ref_found	View field is found, item passed through ref parameter
    found field         If a item was resolved to some field
*/

Field *
find_field_in_tables(Session *session, Item_ident *item,
                     TableList *first_table, TableList *last_table,
		     Item **ref, find_item_error_report_type report_error,
                     bool check_privileges, bool register_tree_change)
{
  Field *found=0;
  const char *db= item->db_name;
  const char *table_name= item->table_name;
  const char *name= item->field_name;
  uint32_t length=(uint32_t) strlen(name);
  char name_buff[NAME_LEN+1];
  TableList *cur_table= first_table;
  TableList *actual_table;
  bool allow_rowid;

  if (!table_name || !table_name[0])
  {
    table_name= 0;                              // For easier test
    db= 0;
  }

  allow_rowid= table_name || (cur_table && !cur_table->next_local);

  if (item->cached_table)
  {
    /*
      This shortcut is used by prepared statements. We assume that
      TableList *first_table is not changed during query execution (which
      is true for all queries except RENAME but luckily RENAME doesn't
      use fields...) so we can rely on reusing pointer to its member.
      With this optimization we also miss case when addition of one more
      field makes some prepared query ambiguous and so erroneous, but we
      accept this trade off.
    */
    TableList *table_ref= item->cached_table;
    /*
      The condition (table_ref->view == NULL) ensures that we will call
      find_field_in_table even in the case of information schema tables
      when table_ref->field_translation != NULL.
      */
    if (table_ref->table)
      found= find_field_in_table(session, table_ref->table, name, length,
                                 true, &(item->cached_field_index));
    else
      found= find_field_in_table_ref(session, table_ref, name, length, item->name,
                                     NULL, NULL, ref, check_privileges,
                                     true, &(item->cached_field_index),
                                     register_tree_change,
                                     &actual_table);
    if (found)
    {
      if (found == WRONG_GRANT)
	return (Field*) 0;

      /*
        Only views fields should be marked as dependent, not an underlying
        fields.
      */
      {
        Select_Lex *current_sel= session->lex->current_select;
        Select_Lex *last_select= table_ref->select_lex;
        /*
          If the field was an outer referencee, mark all selects using this
          sub query as dependent on the outer query
        */
        if (current_sel != last_select)
          mark_select_range_as_dependent(session, last_select, current_sel,
                                         found, *ref, item);
      }
      return found;
    }
  }

  if (db && lower_case_table_names)
  {
    /*
      convert database to lower case for comparison.
      We can't do this in Item_field as this would change the
      'name' of the item which may be used in the select list
    */
    strncpy(name_buff, db, sizeof(name_buff)-1);
    my_casedn_str(files_charset_info, name_buff);
    db= name_buff;
  }

  if (last_table)
    last_table= last_table->next_name_resolution_table;

  for (; cur_table != last_table ;
       cur_table= cur_table->next_name_resolution_table)
  {
    Field *cur_field= find_field_in_table_ref(session, cur_table, name, length,
                                              item->name, db, table_name, ref,
                                              (session->lex->sql_command ==
                                               SQLCOM_SHOW_FIELDS)
                                              ? false : check_privileges,
                                              allow_rowid,
                                              &(item->cached_field_index),
                                              register_tree_change,
                                              &actual_table);
    if (cur_field)
    {
      if (cur_field == WRONG_GRANT)
      {
        if (session->lex->sql_command != SQLCOM_SHOW_FIELDS)
          return (Field*) 0;

        session->clear_error();
        cur_field= find_field_in_table_ref(session, cur_table, name, length,
                                           item->name, db, table_name, ref,
                                           false,
                                           allow_rowid,
                                           &(item->cached_field_index),
                                           register_tree_change,
                                           &actual_table);
        if (cur_field)
        {
          Field *nf=new Field_null(NULL,0,Field::NONE,
                                   cur_field->field_name,
                                   &my_charset_bin);
          nf->init(cur_table->table);
          cur_field= nf;
        }
      }

      /*
        Store the original table of the field, which may be different from
        cur_table in the case of NATURAL/USING join.
      */
      item->cached_table= (!actual_table->cacheable_table || found) ?
                          0 : actual_table;

      assert(session->where);
      /*
        If we found a fully qualified field we return it directly as it can't
        have duplicates.
       */
      if (db)
        return cur_field;

      if (found)
      {
        if (report_error == REPORT_ALL_ERRORS ||
            report_error == IGNORE_EXCEPT_NON_UNIQUE)
          my_error(ER_NON_UNIQ_ERROR, MYF(0),
                   table_name ? item->full_name() : name, session->where);
        return (Field*) 0;
      }
      found= cur_field;
    }
  }

  if (found)
    return found;

  /*
    If the field was qualified and there were no tables to search, issue
    an error that an unknown table was given. The situation is detected
    as follows: if there were no tables we wouldn't go through the loop
    and cur_table wouldn't be updated by the loop increment part, so it
    will be equal to the first table.
  */
  if (table_name && (cur_table == first_table) &&
      (report_error == REPORT_ALL_ERRORS ||
       report_error == REPORT_EXCEPT_NON_UNIQUE))
  {
    char buff[NAME_LEN*2+1];
    if (db && db[0])
    {
      /* We're in an error condition, two extra strlen's aren't going
       * to kill us */
      assert(strlen(db) <= NAME_LEN);
      assert(strlen(table_name) <= NAME_LEN);
      strcpy(buff, db);
      strcat(buff,".");
      strcat(buff, table_name);
      table_name=buff;
    }
    my_error(ER_UNKNOWN_TABLE, MYF(0), table_name, session->where);
  }
  else
  {
    if (report_error == REPORT_ALL_ERRORS ||
        report_error == REPORT_EXCEPT_NON_UNIQUE)
      my_error(ER_BAD_FIELD_ERROR, MYF(0), item->full_name(), session->where);
    else
      found= not_found_field;
  }
  return found;
}


/*
  Find Item in list of items (find_field_in_tables analog)

  TODO
    is it better return only counter?

  SYNOPSIS
    find_item_in_list()
    find			Item to find
    items			List of items
    counter			To return number of found item
    report_error
      REPORT_ALL_ERRORS		report errors, return 0 if error
      REPORT_EXCEPT_NOT_FOUND	Do not report 'not found' error and
				return not_found_item, report other errors,
				return 0
      IGNORE_ERRORS		Do not report errors, return 0 if error
    resolution                  Set to the resolution type if the item is found
                                (it says whether the item is resolved
                                 against an alias name,
                                 or as a field name without alias,
                                 or as a field hidden by alias,
                                 or ignoring alias)

  RETURN VALUES
    0			Item is not found or item is not unique,
			error message is reported
    not_found_item	Function was called with
			report_error == REPORT_EXCEPT_NOT_FOUND and
			item was not found. No error message was reported
                        found field
*/

/* Special Item pointer to serve as a return value from find_item_in_list(). */
Item **not_found_item= (Item**) 0x1;


Item **
find_item_in_list(Item *find, List<Item> &items, uint32_t *counter,
                  find_item_error_report_type report_error,
                  enum_resolution_type *resolution)
{
  List_iterator<Item> li(items);
  Item **found=0, **found_unaliased= 0, *item;
  const char *db_name=0;
  const char *field_name=0;
  const char *table_name=0;
  bool found_unaliased_non_uniq= 0;
  /*
    true if the item that we search for is a valid name reference
    (and not an item that happens to have a name).
  */
  bool is_ref_by_name= 0;
  uint32_t unaliased_counter= 0;

  *resolution= NOT_RESOLVED;

  is_ref_by_name= (find->type() == Item::FIELD_ITEM  ||
                   find->type() == Item::REF_ITEM);
  if (is_ref_by_name)
  {
    field_name= ((Item_ident*) find)->field_name;
    table_name= ((Item_ident*) find)->table_name;
    db_name=    ((Item_ident*) find)->db_name;
  }

  for (uint32_t i= 0; (item=li++); i++)
  {
    if (field_name && item->real_item()->type() == Item::FIELD_ITEM)
    {
      Item_ident *item_field= (Item_ident*) item;

      /*
	In case of group_concat() with ORDER BY condition in the QUERY
	item_field can be field of temporary table without item name
	(if this field created from expression argument of group_concat()),
	=> we have to check presence of name before compare
      */
      if (!item_field->name)
        continue;

      if (table_name)
      {
        /*
          If table name is specified we should find field 'field_name' in
          table 'table_name'. According to SQL-standard we should ignore
          aliases in this case.

          Since we should NOT prefer fields from the select list over
          other fields from the tables participating in this select in
          case of ambiguity we have to do extra check outside this function.

          We use strcmp for table names and database names as these may be
          case sensitive. In cases where they are not case sensitive, they
          are always in lower case.

	  item_field->field_name and item_field->table_name can be 0x0 if
	  item is not fix_field()'ed yet.
        */
        if (item_field->field_name && item_field->table_name &&
	    !my_strcasecmp(system_charset_info, item_field->field_name,
                           field_name) &&
            !my_strcasecmp(table_alias_charset, item_field->table_name,
                           table_name) &&
            (!db_name || (item_field->db_name &&
                          !strcmp(item_field->db_name, db_name))))
        {
          if (found_unaliased)
          {
            if ((*found_unaliased)->eq(item, 0))
              continue;
            /*
              Two matching fields in select list.
              We already can bail out because we are searching through
              unaliased names only and will have duplicate error anyway.
            */
            if (report_error != IGNORE_ERRORS)
              my_error(ER_NON_UNIQ_ERROR, MYF(0),
                       find->full_name(), current_session->where);
            return (Item**) 0;
          }
          found_unaliased= li.ref();
          unaliased_counter= i;
          *resolution= RESOLVED_IGNORING_ALIAS;
          if (db_name)
            break;                              // Perfect match
        }
      }
      else
      {
        int fname_cmp= my_strcasecmp(system_charset_info,
                                     item_field->field_name,
                                     field_name);
        if (!my_strcasecmp(system_charset_info,
                           item_field->name,field_name))
        {
          /*
            If table name was not given we should scan through aliases
            and non-aliased fields first. We are also checking unaliased
            name of the field in then next  else-if, to be able to find
            instantly field (hidden by alias) if no suitable alias or
            non-aliased field was found.
          */
          if (found)
          {
            if ((*found)->eq(item, 0))
              continue;                           // Same field twice
            if (report_error != IGNORE_ERRORS)
              my_error(ER_NON_UNIQ_ERROR, MYF(0),
                       find->full_name(), current_session->where);
            return (Item**) 0;
          }
          found= li.ref();
          *counter= i;
          *resolution= fname_cmp ? RESOLVED_AGAINST_ALIAS:
	                           RESOLVED_WITH_NO_ALIAS;
        }
        else if (!fname_cmp)
        {
          /*
            We will use non-aliased field or react on such ambiguities only if
            we won't be able to find aliased field.
            Again if we have ambiguity with field outside of select list
            we should prefer fields from select list.
          */
          if (found_unaliased)
          {
            if ((*found_unaliased)->eq(item, 0))
              continue;                           // Same field twice
            found_unaliased_non_uniq= 1;
          }
          found_unaliased= li.ref();
          unaliased_counter= i;
        }
      }
    }
    else if (!table_name)
    {
      if (is_ref_by_name && find->name && item->name &&
	  !my_strcasecmp(system_charset_info,item->name,find->name))
      {
        found= li.ref();
        *counter= i;
        *resolution= RESOLVED_AGAINST_ALIAS;
        break;
      }
      else if (find->eq(item,0))
      {
        found= li.ref();
        *counter= i;
        *resolution= RESOLVED_IGNORING_ALIAS;
        break;
      }
    }
  }
  if (!found)
  {
    if (found_unaliased_non_uniq)
    {
      if (report_error != IGNORE_ERRORS)
        my_error(ER_NON_UNIQ_ERROR, MYF(0),
                 find->full_name(), current_session->where);
      return (Item **) 0;
    }
    if (found_unaliased)
    {
      found= found_unaliased;
      *counter= unaliased_counter;
      *resolution= RESOLVED_BEHIND_ALIAS;
    }
  }
  if (found)
    return found;
  if (report_error != REPORT_EXCEPT_NOT_FOUND)
  {
    if (report_error == REPORT_ALL_ERRORS)
      my_error(ER_BAD_FIELD_ERROR, MYF(0),
               find->full_name(), current_session->where);
    return (Item **) 0;
  }
  else
    return (Item **) not_found_item;
}


/*
  Test if a string is a member of a list of strings.

  SYNOPSIS
    test_if_string_in_list()
    find      the string to look for
    str_list  a list of strings to be searched

  DESCRIPTION
    Sequentially search a list of strings for a string, and test whether
    the list contains the same string.

  RETURN
    true  if find is in str_list
    false otherwise
*/

static bool
test_if_string_in_list(const char *find, List<String> *str_list)
{
  List_iterator<String> str_list_it(*str_list);
  String *curr_str;
  size_t find_length= strlen(find);
  while ((curr_str= str_list_it++))
  {
    if (find_length != curr_str->length())
      continue;
    if (!my_strcasecmp(system_charset_info, find, curr_str->ptr()))
      return true;
  }
  return false;
}


/*
  Create a new name resolution context for an item so that it is
  being resolved in a specific table reference.

  SYNOPSIS
    set_new_item_local_context()
    session        pointer to current thread
    item       item for which new context is created and set
    table_ref  table ref where an item showld be resolved

  DESCRIPTION
    Create a new name resolution context for an item, so that the item
    is resolved only the supplied 'table_ref'.

  RETURN
    false  if all OK
    true   otherwise
*/

static bool
set_new_item_local_context(Session *session, Item_ident *item, TableList *table_ref)
{
  Name_resolution_context *context;
  if (!(context= new (session->mem_root) Name_resolution_context))
    return true;
  context->init();
  context->first_name_resolution_table=
    context->last_name_resolution_table= table_ref;
  item->context= context;
  return false;
}


/*
  Find and mark the common columns of two table references.

  SYNOPSIS
    mark_common_columns()
    session                [in] current thread
    table_ref_1        [in] the first (left) join operand
    table_ref_2        [in] the second (right) join operand
    using_fields       [in] if the join is JOIN...USING - the join columns,
                            if NATURAL join, then NULL
    found_using_fields [out] number of fields from the USING clause that were
                             found among the common fields

  DESCRIPTION
    The procedure finds the common columns of two relations (either
    tables or intermediate join results), and adds an equi-join condition
    to the ON clause of 'table_ref_2' for each pair of matching columns.
    If some of table_ref_XXX represents a base table or view, then we
    create new 'Natural_join_column' instances for each column
    reference and store them in the 'join_columns' of the table
    reference.

  IMPLEMENTATION
    The procedure assumes that store_natural_using_join_columns() was
    called for the previous level of NATURAL/USING joins.

  RETURN
    true   error when some common column is non-unique, or out of memory
    false  OK
*/

static bool
mark_common_columns(Session *session, TableList *table_ref_1, TableList *table_ref_2,
                    List<String> *using_fields, uint32_t *found_using_fields)
{
  Field_iterator_table_ref it_1, it_2;
  Natural_join_column *nj_col_1, *nj_col_2;
  bool result= true;
  bool first_outer_loop= true;
  /*
    Leaf table references to which new natural join columns are added
    if the leaves are != NULL.
  */
  TableList *leaf_1= (table_ref_1->nested_join &&
                       !table_ref_1->is_natural_join) ?
                      NULL : table_ref_1;
  TableList *leaf_2= (table_ref_2->nested_join &&
                       !table_ref_2->is_natural_join) ?
                      NULL : table_ref_2;

  *found_using_fields= 0;

  for (it_1.set(table_ref_1); !it_1.end_of_fields(); it_1.next())
  {
    bool found= false;
    const char *field_name_1;
    /* true if field_name_1 is a member of using_fields */
    bool is_using_column_1;
    if (!(nj_col_1= it_1.get_or_create_column_ref(leaf_1)))
      goto err;
    field_name_1= nj_col_1->name();
    is_using_column_1= using_fields &&
      test_if_string_in_list(field_name_1, using_fields);

    /*
      Find a field with the same name in table_ref_2.

      Note that for the second loop, it_2.set() will iterate over
      table_ref_2->join_columns and not generate any new elements or
      lists.
    */
    nj_col_2= NULL;
    for (it_2.set(table_ref_2); !it_2.end_of_fields(); it_2.next())
    {
      Natural_join_column *cur_nj_col_2;
      const char *cur_field_name_2;
      if (!(cur_nj_col_2= it_2.get_or_create_column_ref(leaf_2)))
        goto err;
      cur_field_name_2= cur_nj_col_2->name();

      /*
        Compare the two columns and check for duplicate common fields.
        A common field is duplicate either if it was already found in
        table_ref_2 (then found == true), or if a field in table_ref_2
        was already matched by some previous field in table_ref_1
        (then cur_nj_col_2->is_common == true).
        Note that it is too early to check the columns outside of the
        USING list for ambiguity because they are not actually "referenced"
        here. These columns must be checked only on unqualified reference
        by name (e.g. in SELECT list).
      */
      if (!my_strcasecmp(system_charset_info, field_name_1, cur_field_name_2))
      {
        if (cur_nj_col_2->is_common ||
            (found && (!using_fields || is_using_column_1)))
        {
          my_error(ER_NON_UNIQ_ERROR, MYF(0), field_name_1, session->where);
          goto err;
        }
        nj_col_2= cur_nj_col_2;
        found= true;
      }
    }
    if (first_outer_loop && leaf_2)
    {
      /*
        Make sure that the next inner loop "knows" that all columns
        are materialized already.
      */
      leaf_2->is_join_columns_complete= true;
      first_outer_loop= false;
    }
    if (!found)
      continue;                                 // No matching field

    /*
      field_1 and field_2 have the same names. Check if they are in the USING
      clause (if present), mark them as common fields, and add a new
      equi-join condition to the ON clause.
    */
    if (nj_col_2 && (!using_fields ||is_using_column_1))
    {
      Item *item_1=   nj_col_1->create_item(session);
      Item *item_2=   nj_col_2->create_item(session);
      Field *field_1= nj_col_1->field();
      Field *field_2= nj_col_2->field();
      Item_ident *item_ident_1, *item_ident_2;
      Item_func_eq *eq_cond;

      if (!item_1 || !item_2)
        goto err;                               // out of memory

      /*
        In the case of no_wrap_view_item == 0, the created items must be
        of sub-classes of Item_ident.
      */
      assert(item_1->type() == Item::FIELD_ITEM ||
                  item_1->type() == Item::REF_ITEM);
      assert(item_2->type() == Item::FIELD_ITEM ||
                  item_2->type() == Item::REF_ITEM);

      /*
        We need to cast item_1,2 to Item_ident, because we need to hook name
        resolution contexts specific to each item.
      */
      item_ident_1= (Item_ident*) item_1;
      item_ident_2= (Item_ident*) item_2;
      /*
        Create and hook special name resolution contexts to each item in the
        new join condition . We need this to both speed-up subsequent name
        resolution of these items, and to enable proper name resolution of
        the items during the execute phase of PS.
      */
      if (set_new_item_local_context(session, item_ident_1, nj_col_1->table_ref) ||
          set_new_item_local_context(session, item_ident_2, nj_col_2->table_ref))
        goto err;

      if (!(eq_cond= new Item_func_eq(item_ident_1, item_ident_2)))
        goto err;                               /* Out of memory. */

      /*
        Add the new equi-join condition to the ON clause. Notice that
        fix_fields() is applied to all ON conditions in setup_conds()
        so we don't do it here.
       */
      add_join_on((table_ref_1->outer_join & JOIN_TYPE_RIGHT ?
                   table_ref_1 : table_ref_2),
                  eq_cond);

      nj_col_1->is_common= nj_col_2->is_common= true;

      if (field_1)
      {
        Table *table_1= nj_col_1->table_ref->table;
        /* Mark field_1 used for table cache. */
        bitmap_set_bit(table_1->read_set, field_1->field_index);
        table_1->covering_keys.intersect(field_1->part_of_key);
        table_1->merge_keys.merge(field_1->part_of_key);
      }
      if (field_2)
      {
        Table *table_2= nj_col_2->table_ref->table;
        /* Mark field_2 used for table cache. */
        bitmap_set_bit(table_2->read_set, field_2->field_index);
        table_2->covering_keys.intersect(field_2->part_of_key);
        table_2->merge_keys.merge(field_2->part_of_key);
      }

      if (using_fields != NULL)
        ++(*found_using_fields);
    }
  }
  if (leaf_1)
    leaf_1->is_join_columns_complete= true;

  /*
    Everything is OK.
    Notice that at this point there may be some column names in the USING
    clause that are not among the common columns. This is an SQL error and
    we check for this error in store_natural_using_join_columns() when
    (found_using_fields < length(join_using_fields)).
  */
  result= false;

err:
  return(result);
}



/*
  Materialize and store the row type of NATURAL/USING join.

  SYNOPSIS
    store_natural_using_join_columns()
    session                current thread
    natural_using_join the table reference of the NATURAL/USING join
    table_ref_1        the first (left) operand (of a NATURAL/USING join).
    table_ref_2        the second (right) operand (of a NATURAL/USING join).
    using_fields       if the join is JOIN...USING - the join columns,
                       if NATURAL join, then NULL
    found_using_fields number of fields from the USING clause that were
                       found among the common fields

  DESCRIPTION
    Iterate over the columns of both join operands and sort and store
    all columns into the 'join_columns' list of natural_using_join
    where the list is formed by three parts:
      part1: The coalesced columns of table_ref_1 and table_ref_2,
             sorted according to the column order of the first table.
      part2: The other columns of the first table, in the order in
             which they were defined in CREATE TABLE.
      part3: The other columns of the second table, in the order in
             which they were defined in CREATE TABLE.
    Time complexity - O(N1+N2), where Ni = length(table_ref_i).

  IMPLEMENTATION
    The procedure assumes that mark_common_columns() has been called
    for the join that is being processed.

  RETURN
    true    error: Some common column is ambiguous
    false   OK
*/

static bool
store_natural_using_join_columns(Session *,
                                 TableList *natural_using_join,
                                 TableList *table_ref_1,
                                 TableList *table_ref_2,
                                 List<String> *using_fields,
                                 uint32_t found_using_fields)
{
  Field_iterator_table_ref it_1, it_2;
  Natural_join_column *nj_col_1, *nj_col_2;
  bool result= true;
  List<Natural_join_column> *non_join_columns;

  assert(!natural_using_join->join_columns);

  if (!(non_join_columns= new List<Natural_join_column>) ||
      !(natural_using_join->join_columns= new List<Natural_join_column>))
    goto err;

  /* Append the columns of the first join operand. */
  for (it_1.set(table_ref_1); !it_1.end_of_fields(); it_1.next())
  {
    nj_col_1= it_1.get_natural_column_ref();
    if (nj_col_1->is_common)
    {
      natural_using_join->join_columns->push_back(nj_col_1);
      /* Reset the common columns for the next call to mark_common_columns. */
      nj_col_1->is_common= false;
    }
    else
      non_join_columns->push_back(nj_col_1);
  }

  /*
    Check that all columns in the USING clause are among the common
    columns. If this is not the case, report the first one that was
    not found in an error.
  */
  if (using_fields && found_using_fields < using_fields->elements)
  {
    String *using_field_name;
    List_iterator_fast<String> using_fields_it(*using_fields);
    while ((using_field_name= using_fields_it++))
    {
      const char *using_field_name_ptr= using_field_name->c_ptr();
      List_iterator_fast<Natural_join_column>
        it(*(natural_using_join->join_columns));
      Natural_join_column *common_field;

      for (;;)
      {
        /* If reached the end of fields, and none was found, report error. */
        if (!(common_field= it++))
        {
          my_error(ER_BAD_FIELD_ERROR, MYF(0), using_field_name_ptr,
                   current_session->where);
          goto err;
        }
        if (!my_strcasecmp(system_charset_info,
                           common_field->name(), using_field_name_ptr))
          break;                                // Found match
      }
    }
  }

  /* Append the non-equi-join columns of the second join operand. */
  for (it_2.set(table_ref_2); !it_2.end_of_fields(); it_2.next())
  {
    nj_col_2= it_2.get_natural_column_ref();
    if (!nj_col_2->is_common)
      non_join_columns->push_back(nj_col_2);
    else
    {
      /* Reset the common columns for the next call to mark_common_columns. */
      nj_col_2->is_common= false;
    }
  }

  if (non_join_columns->elements > 0)
    natural_using_join->join_columns->concat(non_join_columns);
  natural_using_join->is_join_columns_complete= true;

  result= false;

err:
  return(result);
}


/*
  Precompute and store the row types of the top-most NATURAL/USING joins.

  SYNOPSIS
    store_top_level_join_columns()
    session            current thread
    table_ref      nested join or table in a FROM clause
    left_neighbor  neighbor table reference to the left of table_ref at the
                   same level in the join tree
    right_neighbor neighbor table reference to the right of table_ref at the
                   same level in the join tree

  DESCRIPTION
    The procedure performs a post-order traversal of a nested join tree
    and materializes the row types of NATURAL/USING joins in a
    bottom-up manner until it reaches the TableList elements that
    represent the top-most NATURAL/USING joins. The procedure should be
    applied to each element of Select_Lex::top_join_list (i.e. to each
    top-level element of the FROM clause).

  IMPLEMENTATION
    Notice that the table references in the list nested_join->join_list
    are in reverse order, thus when we iterate over it, we are moving
    from the right to the left in the FROM clause.

  RETURN
    true   Error
    false  OK
*/

static bool
store_top_level_join_columns(Session *session, TableList *table_ref,
                             TableList *left_neighbor,
                             TableList *right_neighbor)
{
  bool result= true;

  /* Call the procedure recursively for each nested table reference. */
  if (table_ref->nested_join)
  {
    List_iterator_fast<TableList> nested_it(table_ref->nested_join->join_list);
    TableList *same_level_left_neighbor= nested_it++;
    TableList *same_level_right_neighbor= NULL;
    /* Left/right-most neighbors, possibly at higher levels in the join tree. */
    TableList *real_left_neighbor, *real_right_neighbor;

    while (same_level_left_neighbor)
    {
      TableList *cur_table_ref= same_level_left_neighbor;
      same_level_left_neighbor= nested_it++;
      /*
        The order of RIGHT JOIN operands is reversed in 'join list' to
        transform it into a LEFT JOIN. However, in this procedure we need
        the join operands in their lexical order, so below we reverse the
        join operands. Notice that this happens only in the first loop,
        and not in the second one, as in the second loop
        same_level_left_neighbor == NULL.
        This is the correct behavior, because the second loop sets
        cur_table_ref reference correctly after the join operands are
        swapped in the first loop.
      */
      if (same_level_left_neighbor &&
          cur_table_ref->outer_join & JOIN_TYPE_RIGHT)
      {
        /* This can happen only for JOIN ... ON. */
        assert(table_ref->nested_join->join_list.elements == 2);
        std::swap(same_level_left_neighbor, cur_table_ref);
      }

      /*
        Pick the parent's left and right neighbors if there are no immediate
        neighbors at the same level.
      */
      real_left_neighbor=  (same_level_left_neighbor) ?
                           same_level_left_neighbor : left_neighbor;
      real_right_neighbor= (same_level_right_neighbor) ?
                           same_level_right_neighbor : right_neighbor;

      if (cur_table_ref->nested_join &&
          store_top_level_join_columns(session, cur_table_ref,
                                       real_left_neighbor, real_right_neighbor))
        goto err;
      same_level_right_neighbor= cur_table_ref;
    }
  }

  /*
    If this is a NATURAL/USING join, materialize its result columns and
    convert to a JOIN ... ON.
  */
  if (table_ref->is_natural_join)
  {
    assert(table_ref->nested_join &&
                table_ref->nested_join->join_list.elements == 2);
    List_iterator_fast<TableList> operand_it(table_ref->nested_join->join_list);
    /*
      Notice that the order of join operands depends on whether table_ref
      represents a LEFT or a RIGHT join. In a RIGHT join, the operands are
      in inverted order.
     */
    TableList *table_ref_2= operand_it++; /* Second NATURAL join operand.*/
    TableList *table_ref_1= operand_it++; /* First NATURAL join operand. */
    List<String> *using_fields= table_ref->join_using_fields;
    uint32_t found_using_fields;

    /*
      The two join operands were interchanged in the parser, change the order
      back for 'mark_common_columns'.
    */
    if (table_ref_2->outer_join & JOIN_TYPE_RIGHT)
      std::swap(table_ref_1, table_ref_2);
    if (mark_common_columns(session, table_ref_1, table_ref_2,
                            using_fields, &found_using_fields))
      goto err;

    /*
      Swap the join operands back, so that we pick the columns of the second
      one as the coalesced columns. In this way the coalesced columns are the
      same as of an equivalent LEFT JOIN.
    */
    if (table_ref_1->outer_join & JOIN_TYPE_RIGHT)
      std::swap(table_ref_1, table_ref_2);
    if (store_natural_using_join_columns(session, table_ref, table_ref_1,
                                         table_ref_2, using_fields,
                                         found_using_fields))
      goto err;

    /*
      Change NATURAL JOIN to JOIN ... ON. We do this for both operands
      because either one of them or the other is the one with the
      natural join flag because RIGHT joins are transformed into LEFT,
      and the two tables may be reordered.
    */
    table_ref_1->natural_join= table_ref_2->natural_join= NULL;

    /* Add a true condition to outer joins that have no common columns. */
    if (table_ref_2->outer_join &&
        !table_ref_1->on_expr && !table_ref_2->on_expr)
      table_ref_2->on_expr= new Item_int((int64_t) 1,1);   /* Always true. */

    /* Change this table reference to become a leaf for name resolution. */
    if (left_neighbor)
    {
      TableList *last_leaf_on_the_left;
      last_leaf_on_the_left= left_neighbor->last_leaf_for_name_resolution();
      last_leaf_on_the_left->next_name_resolution_table= table_ref;
    }
    if (right_neighbor)
    {
      TableList *first_leaf_on_the_right;
      first_leaf_on_the_right= right_neighbor->first_leaf_for_name_resolution();
      table_ref->next_name_resolution_table= first_leaf_on_the_right;
    }
    else
      table_ref->next_name_resolution_table= NULL;
  }
  result= false; /* All is OK. */

err:
  return(result);
}


/*
  Compute and store the row types of the top-most NATURAL/USING joins
  in a FROM clause.

  SYNOPSIS
    setup_natural_join_row_types()
    session          current thread
    from_clause  list of top-level table references in a FROM clause

  DESCRIPTION
    Apply the procedure 'store_top_level_join_columns' to each of the
    top-level table referencs of the FROM clause. Adjust the list of tables
    for name resolution - context->first_name_resolution_table to the
    top-most, lef-most NATURAL/USING join.

  IMPLEMENTATION
    Notice that the table references in 'from_clause' are in reverse
    order, thus when we iterate over it, we are moving from the right
    to the left in the FROM clause.

  RETURN
    true   Error
    false  OK
*/
static bool setup_natural_join_row_types(Session *session,
                                         List<TableList> *from_clause,
                                         Name_resolution_context *context)
{
  session->where= "from clause";
  if (from_clause->elements == 0)
    return false; /* We come here in the case of UNIONs. */

  List_iterator_fast<TableList> table_ref_it(*from_clause);
  TableList *table_ref; /* Current table reference. */
  /* Table reference to the left of the current. */
  TableList *left_neighbor;
  /* Table reference to the right of the current. */
  TableList *right_neighbor= NULL;

  /* Note that tables in the list are in reversed order */
  for (left_neighbor= table_ref_it++; left_neighbor ; )
  {
    table_ref= left_neighbor;
    left_neighbor= table_ref_it++;
    if (store_top_level_join_columns(session, table_ref,
                                     left_neighbor, right_neighbor))
      return true;
    if (left_neighbor)
    {
      TableList *first_leaf_on_the_right;
      first_leaf_on_the_right= table_ref->first_leaf_for_name_resolution();
      left_neighbor->next_name_resolution_table= first_leaf_on_the_right;
    }
    right_neighbor= table_ref;
  }

  /*
    Store the top-most, left-most NATURAL/USING join, so that we start
    the search from that one instead of context->table_list. At this point
    right_neighbor points to the left-most top-level table reference in the
    FROM clause.
  */
  assert(right_neighbor);
  context->first_name_resolution_table=
    right_neighbor->first_leaf_for_name_resolution();

  return false;
}


/****************************************************************************
** Expand all '*' in given fields
****************************************************************************/

int setup_wild(Session *session,
               TableList *,
               List<Item> &fields,
               List<Item> *sum_func_list,
               uint32_t wild_num)
{
  if (!wild_num)
    return(0);

  Item *item;
  List_iterator<Item> it(fields);

  session->lex->current_select->cur_pos_in_select_list= 0;
  while (wild_num && (item= it++))
  {
    if (item->type() == Item::FIELD_ITEM &&
        ((Item_field*) item)->field_name &&
	((Item_field*) item)->field_name[0] == '*' &&
	!((Item_field*) item)->field)
    {
      uint32_t elem= fields.elements;
      bool any_privileges= ((Item_field *) item)->any_privileges;
      Item_subselect *subsel= session->lex->current_select->master_unit()->item;
      if (subsel &&
          subsel->substype() == Item_subselect::EXISTS_SUBS)
      {
        /*
          It is EXISTS(SELECT * ...) and we can replace * by any constant.

          Item_int do not need fix_fields() because it is basic constant.
        */
        it.replace(new Item_int("Not_used", (int64_t) 1,
                                MY_INT64_NUM_DECIMAL_DIGITS));
      }
      else if (insert_fields(session, ((Item_field*) item)->context,
                             ((Item_field*) item)->db_name,
                             ((Item_field*) item)->table_name, &it,
                             any_privileges))
      {
	return(-1);
      }
      if (sum_func_list)
      {
	/*
	  sum_func_list is a list that has the fields list as a tail.
	  Because of this we have to update the element count also for this
	  list after expanding the '*' entry.
	*/
	sum_func_list->elements+= fields.elements - elem;
      }
      wild_num--;
    }
    else
      session->lex->current_select->cur_pos_in_select_list++;
  }
  session->lex->current_select->cur_pos_in_select_list= UNDEF_POS;
  return(0);
}

/****************************************************************************
** Check that all given fields exists and fill struct with current data
****************************************************************************/

bool setup_fields(Session *session, Item **ref_pointer_array,
                  List<Item> &fields, enum_mark_columns mark_used_columns,
                  List<Item> *sum_func_list, bool allow_sum_func)
{
  register Item *item;
  enum_mark_columns save_mark_used_columns= session->mark_used_columns;
  nesting_map save_allow_sum_func= session->lex->allow_sum_func;
  List_iterator<Item> it(fields);
  bool save_is_item_list_lookup;

  session->mark_used_columns= mark_used_columns;
  if (allow_sum_func)
    session->lex->allow_sum_func|= 1 << session->lex->current_select->nest_level;
  session->where= Session::DEFAULT_WHERE;
  save_is_item_list_lookup= session->lex->current_select->is_item_list_lookup;
  session->lex->current_select->is_item_list_lookup= 0;

  /*
    To prevent fail on forward lookup we fill it with zerows,
    then if we got pointer on zero after find_item_in_list we will know
    that it is forward lookup.

    There is other way to solve problem: fill array with pointers to list,
    but it will be slower.

    TODO: remove it when (if) we made one list for allfields and
    ref_pointer_array
  */
  if (ref_pointer_array)
    memset(ref_pointer_array, 0, sizeof(Item *) * fields.elements);

  Item **ref= ref_pointer_array;
  session->lex->current_select->cur_pos_in_select_list= 0;
  while ((item= it++))
  {
    if ((!item->fixed && item->fix_fields(session, it.ref())) || (item= *(it.ref()))->check_cols(1))
    {
      session->lex->current_select->is_item_list_lookup= save_is_item_list_lookup;
      session->lex->allow_sum_func= save_allow_sum_func;
      session->mark_used_columns= save_mark_used_columns;
      return(true); /* purecov: inspected */
    }
    if (ref)
      *(ref++)= item;
    if (item->with_sum_func && item->type() != Item::SUM_FUNC_ITEM &&
	sum_func_list)
      item->split_sum_func(session, ref_pointer_array, *sum_func_list);
    session->used_tables|= item->used_tables();
    session->lex->current_select->cur_pos_in_select_list++;
  }
  session->lex->current_select->is_item_list_lookup= save_is_item_list_lookup;
  session->lex->current_select->cur_pos_in_select_list= UNDEF_POS;

  session->lex->allow_sum_func= save_allow_sum_func;
  session->mark_used_columns= save_mark_used_columns;
  return(test(session->is_error()));
}


/*
  make list of leaves of join table tree

  SYNOPSIS
    make_leaves_list()
    list    pointer to pointer on list first element
    tables  table list

  RETURN pointer on pointer to next_leaf of last element
*/

TableList **make_leaves_list(TableList **list, TableList *tables)
{
  for (TableList *table= tables; table; table= table->next_local)
  {
    {
      *list= table;
      list= &table->next_leaf;
    }
  }
  return list;
}

/*
  prepare tables

  SYNOPSIS
    setup_tables()
    session		  Thread handler
    context       name resolution contest to setup table list there
    from_clause   Top-level list of table references in the FROM clause
    tables	  Table list (select_lex->table_list)
    leaves        List of join table leaves list (select_lex->leaf_tables)
    refresh       It is onle refresh for subquery
    select_insert It is SELECT ... INSERT command

  NOTE
    Check also that the 'used keys' and 'ignored keys' exists and set up the
    table structure accordingly.
    Create a list of leaf tables. For queries with NATURAL/USING JOINs,
    compute the row types of the top most natural/using join table references
    and link these into a list of table references for name resolution.

    This has to be called for all tables that are used by items, as otherwise
    table->map is not set and all Item_field will be regarded as const items.

  RETURN
    false ok;  In this case *map will includes the chosen index
    true  error
*/

bool setup_tables(Session *session, Name_resolution_context *context,
                  List<TableList> *from_clause, TableList *tables,
                  TableList **leaves, bool select_insert)
{
  uint32_t tablenr= 0;

  assert ((select_insert && !tables->next_name_resolution_table) || !tables ||
               (context->table_list && context->first_name_resolution_table));
  /*
    this is used for INSERT ... SELECT.
    For select we setup tables except first (and its underlying tables)
  */
  TableList *first_select_table= (select_insert ?
                                   tables->next_local:
                                   0);
  if (!(*leaves))
    make_leaves_list(leaves, tables);

  TableList *table_list;
  for (table_list= *leaves;
       table_list;
       table_list= table_list->next_leaf, tablenr++)
  {
    Table *table= table_list->table;
    table->pos_in_table_list= table_list;
    if (first_select_table &&
        table_list->top_table() == first_select_table)
    {
      /* new counting for SELECT of INSERT ... SELECT command */
      first_select_table= 0;
      tablenr= 0;
    }
    table->setup_table_map(table_list, tablenr);
    if (table_list->process_index_hints(table))
      return(1);
  }
  if (tablenr > MAX_TABLES)
  {
    my_error(ER_TOO_MANY_TABLES,MYF(0),MAX_TABLES);
    return(1);
  }

  /* Precompute and store the row types of NATURAL/USING joins. */
  if (setup_natural_join_row_types(session, from_clause, context))
    return(1);

  return(0);
}


/*
  prepare tables and check access for the view tables

  SYNOPSIS
    setup_tables_and_check_view_access()
    session		  Thread handler
    context       name resolution contest to setup table list there
    from_clause   Top-level list of table references in the FROM clause
    tables	  Table list (select_lex->table_list)
    conds	  Condition of current SELECT (can be changed by VIEW)
    leaves        List of join table leaves list (select_lex->leaf_tables)
    refresh       It is onle refresh for subquery
    select_insert It is SELECT ... INSERT command
    want_access   what access is needed

  NOTE
    a wrapper for check_tables that will also check the resulting
    table leaves list for access to all the tables that belong to a view

  RETURN
    false ok;  In this case *map will include the chosen index
    true  error
*/
bool setup_tables_and_check_access(Session *session,
                                   Name_resolution_context *context,
                                   List<TableList> *from_clause,
                                   TableList *tables,
                                   TableList **leaves,
                                   bool select_insert)
{
  TableList *leaves_tmp= NULL;
  bool first_table= true;

  if (setup_tables(session, context, from_clause, tables,
                   &leaves_tmp, select_insert))
    return true;

  if (leaves)
    *leaves= leaves_tmp;

  for (; leaves_tmp; leaves_tmp= leaves_tmp->next_leaf)
  {
    first_table= 0;
  }
  return false;
}


/*
   Create a key_map from a list of index names

   SYNOPSIS
     get_key_map_from_key_list()
     map		key_map to fill in
     table		Table
     index_list		List of index names

   RETURN
     0	ok;  In this case *map will includes the choosed index
     1	error
*/

bool get_key_map_from_key_list(key_map *map, Table *table,
                               List<String> *index_list)
{
  List_iterator_fast<String> it(*index_list);
  String *name;
  uint32_t pos;

  map->clear_all();
  while ((name=it++))
  {
    if (table->s->keynames.type_names == 0 ||
        (pos= find_type(&table->s->keynames, name->ptr(),
                        name->length(), 1)) <=
        0)
    {
      my_error(ER_KEY_DOES_NOT_EXITS, MYF(0), name->c_ptr(),
	       table->pos_in_table_list->alias);
      map->set_all();
      return 1;
    }
    map->set_bit(pos-1);
  }
  return 0;
}


/*
  Drops in all fields instead of current '*' field

  SYNOPSIS
    insert_fields()
    session			Thread handler
    context             Context for name resolution
    db_name		Database name in case of 'database_name.table_name.*'
    table_name		Table name in case of 'table_name.*'
    it			Pointer to '*'
    any_privileges	0 If we should ensure that we have SELECT privileges
		          for all columns
                        1 If any privilege is ok
  RETURN
    0	ok     'it' is updated to point at last inserted
    1	error.  Error message is generated but not sent to client
*/

bool
insert_fields(Session *session, Name_resolution_context *context, const char *db_name,
              const char *table_name, List_iterator<Item> *it,
              bool )
{
  Field_iterator_table_ref field_iterator;
  bool found;
  char name_buff[NAME_LEN+1];

  if (db_name && lower_case_table_names)
  {
    /*
      convert database to lower case for comparison
      We can't do this in Item_field as this would change the
      'name' of the item which may be used in the select list
    */
    strncpy(name_buff, db_name, sizeof(name_buff)-1);
    my_casedn_str(files_charset_info, name_buff);
    db_name= name_buff;
  }

  found= false;

  /*
    If table names are qualified, then loop over all tables used in the query,
    else treat natural joins as leaves and do not iterate over their underlying
    tables.
  */
  for (TableList *tables= (table_name ? context->table_list :
                            context->first_name_resolution_table);
       tables;
       tables= (table_name ? tables->next_local :
                tables->next_name_resolution_table)
       )
  {
    Field *field;
    Table *table= tables->table;

    assert(tables->is_leaf_for_name_resolution());

    if ((table_name && my_strcasecmp(table_alias_charset, table_name, tables->alias)) ||
        (db_name && strcmp(tables->db,db_name)))
      continue;

    /*
      Update the tables used in the query based on the referenced fields. For
      views and natural joins this update is performed inside the loop below.
    */
    if (table)
      session->used_tables|= table->map;

    /*
      Initialize a generic field iterator for the current table reference.
      Notice that it is guaranteed that this iterator will iterate over the
      fields of a single table reference, because 'tables' is a leaf (for
      name resolution purposes).
    */
    field_iterator.set(tables);

    for (; !field_iterator.end_of_fields(); field_iterator.next())
    {
      Item *item;

      if (!(item= field_iterator.create_item(session)))
        return(true);

      if (!found)
      {
        found= true;
        it->replace(item); /* Replace '*' with the first found item. */
      }
      else
        it->after(item);   /* Add 'item' to the SELECT list. */

      if ((field= field_iterator.field()))
      {
        /* Mark fields as used to allow storage engine to optimze access */
        bitmap_set_bit(field->table->read_set, field->field_index);
        /*
          Mark virtual fields for write and others that the virtual fields
          depend on for read.
        */
        if (field->vcol_info)
        {
          Item *vcol_item= field->vcol_info->expr_item;
          assert(vcol_item);
          vcol_item->walk(&Item::register_field_in_read_map, 1, (unsigned char *) 0);
          bitmap_set_bit(field->table->write_set, field->field_index);
        }
        if (table)
        {
          table->covering_keys.intersect(field->part_of_key);
          table->merge_keys.merge(field->part_of_key);
        }
        if (tables->is_natural_join)
        {
          Table *field_table;
          /*
            In this case we are sure that the column ref will not be created
            because it was already created and stored with the natural join.
          */
          Natural_join_column *nj_col;
          if (!(nj_col= field_iterator.get_natural_column_ref()))
            return(true);
          assert(nj_col->table_field);
          field_table= nj_col->table_ref->table;
          if (field_table)
          {
            session->used_tables|= field_table->map;
            field_table->covering_keys.intersect(field->part_of_key);
            field_table->merge_keys.merge(field->part_of_key);
            field_table->used_fields++;
          }
        }
      }
      else
        session->used_tables|= item->used_tables();
      session->lex->current_select->cur_pos_in_select_list++;
    }
    /*
      In case of stored tables, all fields are considered as used,
      while in the case of views, the fields considered as used are the
      ones marked in setup_tables during fix_fields of view columns.
      For NATURAL joins, used_tables is updated in the IF above.
    */
    if (table)
      table->used_fields= table->s->fields;
  }
  if (found)
    return(false);

  /*
    TODO: in the case when we skipped all columns because there was a
    qualified '*', and all columns were coalesced, we have to give a more
    meaningful message than ER_BAD_TABLE_ERROR.
  */
  if (!table_name)
    my_message(ER_NO_TABLES_USED, ER(ER_NO_TABLES_USED), MYF(0));
  else
    my_error(ER_BAD_TABLE_ERROR, MYF(0), table_name);

  return(true);
}


/*
  Fix all conditions and outer join expressions.

  SYNOPSIS
    setup_conds()
    session     thread handler
    tables  list of tables for name resolving (select_lex->table_list)
    leaves  list of leaves of join table tree (select_lex->leaf_tables)
    conds   WHERE clause

  DESCRIPTION
    TODO

  RETURN
    true  if some error occured (e.g. out of memory)
    false if all is OK
*/

int setup_conds(Session *session, TableList *,
                TableList *leaves,
                COND **conds)
{
  Select_Lex *select_lex= session->lex->current_select;
  TableList *table= NULL;	// For HP compilers
  void *save_session_marker= session->session_marker;
  /*
    it_is_update set to true when tables of primary Select_Lex (Select_Lex
    which belong to LEX, i.e. most up SELECT) will be updated by
    INSERT/UPDATE/LOAD
    NOTE: using this condition helps to prevent call of prepare_check_option()
    from subquery of VIEW, because tables of subquery belongs to VIEW
    (see condition before prepare_check_option() call)
  */
  bool save_is_item_list_lookup= select_lex->is_item_list_lookup;
  select_lex->is_item_list_lookup= 0;

  session->mark_used_columns= MARK_COLUMNS_READ;
  select_lex->cond_count= 0;
  select_lex->between_count= 0;
  select_lex->max_equal_elems= 0;

  session->session_marker= (void*)1;
  if (*conds)
  {
    session->where="where clause";
    if ((!(*conds)->fixed && (*conds)->fix_fields(session, conds)) ||
	(*conds)->check_cols(1))
      goto err_no_arena;
  }
  session->session_marker= save_session_marker;

  /*
    Apply fix_fields() to all ON clauses at all levels of nesting,
    including the ones inside view definitions.
  */
  for (table= leaves; table; table= table->next_leaf)
  {
    TableList *embedded; /* The table at the current level of nesting. */
    TableList *embedding= table; /* The parent nested table reference. */
    do
    {
      embedded= embedding;
      if (embedded->on_expr)
      {
        /* Make a join an a expression */
        session->session_marker= (void*)embedded;
        session->where="on clause";
        if ((!embedded->on_expr->fixed && embedded->on_expr->fix_fields(session, &embedded->on_expr)) ||
	    embedded->on_expr->check_cols(1))
	  goto err_no_arena;
        select_lex->cond_count++;
      }
      embedding= embedded->embedding;
    }
    while (embedding &&
           embedding->nested_join->join_list.head() == embedded);

  }
  session->session_marker= save_session_marker;

  session->lex->current_select->is_item_list_lookup= save_is_item_list_lookup;
  return(test(session->is_error()));

err_no_arena:
  select_lex->is_item_list_lookup= save_is_item_list_lookup;
  return(1);
}


/******************************************************************************
** Fill a record with data (for INSERT or UPDATE)
** Returns : 1 if some field has wrong type
******************************************************************************/


/*
  Fill fields with given items.

  SYNOPSIS
    fill_record()
    session           thread handler
    fields        Item_fields list to be filled
    values        values to fill with
    ignore_errors true if we should ignore errors

  NOTE
    fill_record() may set table->auto_increment_field_not_null and a
    caller should make sure that it is reset after their last call to this
    function.

  RETURN
    false   OK
    true    error occured
*/

bool
fill_record(Session * session, List<Item> &fields, List<Item> &values, bool ignore_errors)
{
  List_iterator_fast<Item> f(fields),v(values);
  Item *value, *fld;
  Item_field *field;
  Table *table= 0;
  List<Table> tbl_list;
  bool abort_on_warning_saved= session->abort_on_warning;
  tbl_list.empty();

  /*
    Reset the table->auto_increment_field_not_null as it is valid for
    only one row.
  */
  if (fields.elements)
  {
    /*
      On INSERT or UPDATE fields are checked to be from the same table,
      thus we safely can take table from the first field.
    */
    fld= (Item_field*)f++;
    if (!(field= fld->filed_for_view_update()))
    {
      my_error(ER_NONUPDATEABLE_COLUMN, MYF(0), fld->name);
      goto err;
    }
    table= field->field->table;
    table->auto_increment_field_not_null= false;
    f.rewind();
  }
  while ((fld= f++))
  {
    if (!(field= fld->filed_for_view_update()))
    {
      my_error(ER_NONUPDATEABLE_COLUMN, MYF(0), fld->name);
      goto err;
    }
    value=v++;
    Field *rfield= field->field;
    table= rfield->table;
    if (rfield == table->next_number_field)
      table->auto_increment_field_not_null= true;
    if (rfield->vcol_info &&
        value->type() != Item::DEFAULT_VALUE_ITEM &&
        value->type() != Item::NULL_ITEM &&
        table->s->table_category != TABLE_CATEGORY_TEMPORARY)
    {
      session->abort_on_warning= false;
      push_warning_printf(session, DRIZZLE_ERROR::WARN_LEVEL_WARN,
                          ER_WARNING_NON_DEFAULT_VALUE_FOR_VIRTUAL_COLUMN,
                          ER(ER_WARNING_NON_DEFAULT_VALUE_FOR_VIRTUAL_COLUMN),
                          rfield->field_name, table->s->table_name.str);
      session->abort_on_warning= abort_on_warning_saved;
    }
    if ((value->save_in_field(rfield, 0) < 0) && !ignore_errors)
    {
      my_message(ER_UNKNOWN_ERROR, ER(ER_UNKNOWN_ERROR), MYF(0));
      goto err;
    }
    tbl_list.push_back(table);
  }
  /* Update virtual fields*/
  session->abort_on_warning= false;
  if (tbl_list.head())
  {
    List_iterator_fast<Table> t(tbl_list);
    Table *prev_table= 0;
    while ((table= t++))
    {
      /*
        Do simple optimization to prevent unnecessary re-generating
        values for virtual fields
      */
      if (table != prev_table)
      {
        prev_table= table;
        if (table->vfield)
        {
          if (update_virtual_fields_marked_for_write(table, false))
            goto err;
        }
      }
    }
  }
  session->abort_on_warning= abort_on_warning_saved;
  return(session->is_error());
err:
  session->abort_on_warning= abort_on_warning_saved;
  if (table)
    table->auto_increment_field_not_null= false;
  return(true);
}


/*
  Fill field buffer with values from Field list

  SYNOPSIS
    fill_record()
    session           thread handler
    ptr           pointer on pointer to record
    values        list of fields
    ignore_errors true if we should ignore errors

  NOTE
    fill_record() may set table->auto_increment_field_not_null and a
    caller should make sure that it is reset after their last call to this
    function.

  RETURN
    false   OK
    true    error occured
*/

bool
fill_record(Session *session, Field **ptr, List<Item> &values,
            bool )
{
  List_iterator_fast<Item> v(values);
  Item *value;
  Table *table= 0;
  Field *field;
  List<Table> tbl_list;
  bool abort_on_warning_saved= session->abort_on_warning;

  tbl_list.empty();
  /*
    Reset the table->auto_increment_field_not_null as it is valid for
    only one row.
  */
  if (*ptr)
  {
    /*
      On INSERT or UPDATE fields are checked to be from the same table,
      thus we safely can take table from the first field.
    */
    table= (*ptr)->table;
    table->auto_increment_field_not_null= false;
  }
  while ((field = *ptr++) && ! session->is_error())
  {
    value=v++;
    table= field->table;
    if (field == table->next_number_field)
      table->auto_increment_field_not_null= true;
    if (field->vcol_info &&
        value->type() != Item::DEFAULT_VALUE_ITEM &&
        value->type() != Item::NULL_ITEM &&
        table->s->table_category != TABLE_CATEGORY_TEMPORARY)
    {
      session->abort_on_warning= false;
      push_warning_printf(session, DRIZZLE_ERROR::WARN_LEVEL_WARN,
                          ER_WARNING_NON_DEFAULT_VALUE_FOR_VIRTUAL_COLUMN,
                          ER(ER_WARNING_NON_DEFAULT_VALUE_FOR_VIRTUAL_COLUMN),
                          field->field_name, table->s->table_name.str);
      session->abort_on_warning= abort_on_warning_saved;
    }
    if (value->save_in_field(field, 0) < 0)
      goto err;
    tbl_list.push_back(table);
  }
  /* Update virtual fields*/
  session->abort_on_warning= false;
  if (tbl_list.head())
  {
    List_iterator_fast<Table> t(tbl_list);
    Table *prev_table= 0;
    while ((table= t++))
    {
      /*
        Do simple optimization to prevent unnecessary re-generating
        values for virtual fields
      */
      if (table != prev_table)
      {
        prev_table= table;
        if (table->vfield)
        {
          if (update_virtual_fields_marked_for_write(table, false))
          {
            goto err;
          }
        }
      }
    }
  }
  session->abort_on_warning= abort_on_warning_saved;
  return(session->is_error());

err:
  session->abort_on_warning= abort_on_warning_saved;
  if (table)
    table->auto_increment_field_not_null= false;
  return(true);
}


bool drizzle_rm_tmp_tables(void)
{
  uint32_t  idx;
  char	filePath[FN_REFLEN], filePathCopy[FN_REFLEN];
  MY_DIR *dirp;
  FILEINFO *file;
  TABLE_SHARE share;
  Session *session;

  assert(drizzle_tmpdir);

  if (!(session= new Session))
    return true;
  session->thread_stack= (char*) &session;
  session->store_globals();

  /* Remove all temp tables in the tmpdir */
  /* See if the directory exists */
  if ((dirp = my_dir(drizzle_tmpdir ,MYF(MY_WME | MY_DONT_SORT))))
  {
    /* Remove all SQLxxx tables from directory */
    for (idx=0 ; idx < (uint32_t) dirp->number_off_files ; idx++)
    {
      file=dirp->dir_entry+idx;

      /* skiping . and .. */
      if (file->name[0] == '.' && (!file->name[1] ||
                                   (file->name[1] == '.' &&  !file->name[2])))
        continue;

      if (!memcmp(file->name, TMP_FILE_PREFIX, TMP_FILE_PREFIX_LENGTH))
      {
        char *ext= fn_ext(file->name);
        uint32_t ext_len= strlen(ext);
        uint32_t filePath_len= snprintf(filePath, sizeof(filePath),
                                        "%s%c%s", drizzle_tmpdir, FN_LIBCHAR,
                                        file->name);
        if (!memcmp(".dfe", ext, ext_len))
        {
          handler *handler_file= 0;
          /* We should cut file extention before deleting of table */
          memcpy(filePathCopy, filePath, filePath_len - ext_len);
          filePathCopy[filePath_len - ext_len]= 0;
          init_tmp_table_share(session, &share, "", 0, "", filePathCopy);
          if (!open_table_def(session, &share, 0) &&
              ((handler_file= get_new_handler(&share, session->mem_root,
                                              share.db_type()))))
          {
            handler_file->ha_delete_table(filePathCopy);
            delete handler_file;
          }
          free_table_share(&share);
        }
        /*
          File can be already deleted by tmp_table.file->delete_table().
          So we hide error messages which happnes during deleting of these
          files(MYF(0)).
        */
        my_delete(filePath, MYF(0));
      }
    }
    my_dirend(dirp);
  }

  delete session;

  return false;
}



/*****************************************************************************
	unireg support functions
*****************************************************************************/

/*
  Invalidate any cache entries that are for some DB

  SYNOPSIS
    remove_db_from_cache()
    db		Database name. This will be in lower case if
		lower_case_table_name is set

  NOTE:
  We can't use hash_delete when looping hash_elements. We mark them first
  and afterwards delete those marked unused.
*/

void remove_db_from_cache(const char *db)
{
  for (uint32_t idx=0 ; idx < open_cache.records ; idx++)
  {
    Table *table=(Table*) hash_element(&open_cache,idx);
    if (!strcmp(table->s->db.str, db))
    {
      table->s->version= 0L;			/* Free when thread is ready */
      if (!table->in_use)
	relink_unused(table);
    }
  }
  while (unused_tables && !unused_tables->s->version)
    hash_delete(&open_cache,(unsigned char*) unused_tables);
}


/*
  free all unused tables

  NOTE
    This is called by 'handle_manager' when one wants to periodicly flush
    all not used tables.
*/

void flush_tables()
{
  (void) pthread_mutex_lock(&LOCK_open);
  while (unused_tables)
    hash_delete(&open_cache,(unsigned char*) unused_tables);
  (void) pthread_mutex_unlock(&LOCK_open);
}


/*
  Mark all entries with the table as deleted to force an reopen of the table

  The table will be closed (not stored in cache) by the current thread when
  close_thread_tables() is called.

  PREREQUISITES
    Lock on LOCK_open()

  RETURN
    0  This thread now have exclusive access to this table and no other thread
       can access the table until close_thread_tables() is called.
    1  Table is in use by another thread
*/

bool remove_table_from_cache(Session *session, const char *db, const char *table_name,
                             uint32_t flags)
{
  char key[MAX_DBKEY_LENGTH];
  char *key_pos= key;
  uint32_t key_length;
  Table *table;
  TABLE_SHARE *share;
  bool result= 0, signalled= 0;

  key_pos= strcpy(key_pos, db) + strlen(db);
  key_pos= strcpy(key_pos+1, table_name) + strlen(table_name);
  key_length= (uint32_t) (key_pos-key)+1;

  for (;;)
  {
    HASH_SEARCH_STATE state;
    result= signalled= 0;

    for (table= (Table*) hash_first(&open_cache, (unsigned char*) key, key_length,
                                    &state);
         table;
         table= (Table*) hash_next(&open_cache, (unsigned char*) key, key_length,
                                   &state))
    {
      Session *in_use;

      table->s->version=0L;		/* Free when thread is ready */
      if (!(in_use=table->in_use))
      {
        relink_unused(table);
      }
      else if (in_use != session)
      {
        /*
          Mark that table is going to be deleted from cache. This will
          force threads that are in mysql_lock_tables() (but not yet
          in thr_multi_lock()) to abort it's locks, close all tables and retry
        */
        in_use->some_tables_deleted= 1;
        if (table->is_name_opened())
        {
  	  result=1;
        }
        /*
	  Now we must abort all tables locks used by this thread
	  as the thread may be waiting to get a lock for another table.
          Note that we need to hold LOCK_open while going through the
          list. So that the other thread cannot change it. The other
          thread must also hold LOCK_open whenever changing the
          open_tables list. Aborting the MERGE lock after a child was
          closed and before the parent is closed would be fatal.
        */
        for (Table *session_table= in_use->open_tables;
	     session_table ;
	     session_table= session_table->next)
        {
          /* Do not handle locks of MERGE children. */
	  if (session_table->db_stat)	// If table is open
	    signalled|= mysql_lock_abort_for_thread(session, session_table);
        }
      }
      else
        result= result || (flags & RTFC_OWNED_BY_Session_FLAG);
    }
    while (unused_tables && !unused_tables->s->version)
      hash_delete(&open_cache,(unsigned char*) unused_tables);

    /* Remove table from table definition cache if it's not in use */
    if ((share= (TABLE_SHARE*) hash_search(&table_def_cache,(unsigned char*) key,
                                           key_length)))
    {
      share->version= 0;                          // Mark for delete
      if (share->ref_count == 0)
      {
        pthread_mutex_lock(&share->mutex);
        hash_delete(&table_def_cache, (unsigned char*) share);
      }
    }

    if (result && (flags & RTFC_WAIT_OTHER_THREAD_FLAG))
    {
      /*
        Signal any thread waiting for tables to be freed to
        reopen their tables
      */
      broadcast_refresh();
      if (!(flags & RTFC_CHECK_KILLED_FLAG) || !session->killed)
      {
        dropping_tables++;
        if (likely(signalled))
          (void) pthread_cond_wait(&COND_refresh, &LOCK_open);
        else
        {
          struct timespec abstime;
          /*
            It can happen that another thread has opened the
            table but has not yet locked any table at all. Since
            it can be locked waiting for a table that our thread
            has done LOCK Table x WRITE on previously, we need to
            ensure that the thread actually hears our signal
            before we go to sleep. Thus we wait for a short time
            and then we retry another loop in the
            remove_table_from_cache routine.
          */
          set_timespec(abstime, 10);
          pthread_cond_timedwait(&COND_refresh, &LOCK_open, &abstime);
        }
        dropping_tables--;
        continue;
      }
    }
    break;
  }
  return(result);
}


bool is_equal(const LEX_STRING *a, const LEX_STRING *b)
{
  return a->length == b->length && !strncmp(a->str, b->str, a->length);
}
/**
  @} (end of group Data_Dictionary)
*/

void kill_drizzle(void)
{
  pthread_kill(signal_thread, SIGTERM);
  shutdown_in_progress= 1;			// Safety if kill didn't work
}