~drizzle-trunk/drizzle/development

/* 

    Copyright (C) 2011 Brian Aker

    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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA */

/**

  @file

  @note this is out of date, just for historical reference 

  Locking functions for drizzled.

  Because of the new concurrent inserts, we must first get external locks

  before getting internal locks.  If we do it in the other order, the status

  information is not up to date when called from the lock handler.

  GENERAL DESCRIPTION OF LOCKING

  When not using LOCK TABLES:

  - For each SQL statement lockTables() is called for all involved

    tables.

    - lockTables() will call

      cursor->external_lock(session,locktype) for each table.

      This is followed by a call to thr_multi_lock() for all tables.

  - When statement is done, we call unlockTables().

    This will call DrizzleLock::unlock() followed by

    table_handler->external_lock(session, F_UNLCK) for each table.

  - Note that unlockTables() may be called several times as

    MySQL in some cases can free some tables earlier than others.

  - The above is true both for normal and temporary tables.

  - Temporary non transactional tables are never passed to thr_multi_lock()

    and we never call external_lock(session, F_UNLOCK) on these.

  When using LOCK TABLES:

  - LOCK Table will call lockTables() for all tables.

    lockTables() will call

    table_handler->external_lock(session,locktype) for each table.

    This is followed by a call to thr_multi_lock() for all tables.

  - For each statement, we will call table_handler->start_stmt(Session)

    to inform the table handler that we are using the table.

    The tables used can only be tables used in LOCK TABLES or a

    temporary table.

  - When statement is done, we will call ha_commit_stmt(session);

  - When calling UNLOCK TABLES we call unlockTables() for all

    tables used in LOCK TABLES

  If table_handler->external_lock(session, locktype) fails, we call

  table_handler->external_lock(session, F_UNLCK) for each table that was locked,

  excluding one that caused failure. That means handler must cleanup itself

  in case external_lock() fails.

  @todo

  Change to use malloc() ONLY when using LOCK TABLES command or when

  we are forced to use mysql_lock_merge.

*/

#include <config.h>

#include <fcntl.h>

#include <drizzled/error.h>

#include <drizzled/thr_lock.h>

#include <drizzled/session.h>

#include <drizzled/session/times.h>

#include <drizzled/sql_base.h>

#include <drizzled/lock.h>

#include <drizzled/pthread_globals.h>

#include <drizzled/internal/my_sys.h>

#include <drizzled/pthread_globals.h>

#include <drizzled/plugin/storage_engine.h>

#include <drizzled/util/test.h>

#include <drizzled/open_tables_state.h>

#include <drizzled/table/cache.h>

#include <set>

#include <vector>

#include <algorithm>

#include <functional>

#include <boost/thread/shared_mutex.hpp>

#include <boost/thread/condition_variable.hpp>

using namespace std;

namespace drizzled

{

static boost::mutex LOCK_global_read_lock;

static boost::condition_variable_any COND_global_read_lock;

/**

  @defgroup Locking Locking

  @{

*/

static void print_lock_error(int error, const char *);

/*

  Lock tables.

  SYNOPSIS

    lockTables()

    tables                      An array of pointers to the tables to lock.

    count                       The number of tables to lock.

    flags                       Options:

      DRIZZLE_LOCK_IGNORE_GLOBAL_READ_LOCK      Ignore a global read lock

      DRIZZLE_LOCK_IGNORE_FLUSH                 Ignore a flush tables.

      DRIZZLE_LOCK_NOTIFY_IF_NEED_REOPEN        Instead of reopening altered

                                              or dropped tables by itself,

                                              lockTables() should

                                              notify upper level and rely

                                              on caller doing this.

  RETURN

    A lock structure pointer on success.

    NULL on error or if some tables should be reopen.

*/

/* Map the return value of thr_lock to an error from errmsg.txt */

static drizzled::error_t thr_lock_errno_to_mysql[]=

{ EE_OK, EE_ERROR_FIRST, ER_LOCK_WAIT_TIMEOUT, ER_LOCK_DEADLOCK };

/**

  Reset lock type in lock data and free.

  @param mysql_lock Lock structures to reset.

  @note After a locking error we want to quit the locking of the table(s).

        The test case in the bug report for Bug #18544 has the following

        cases: 1. Locking error in lock_external() due to InnoDB timeout.

        2. Locking error in get_lock_data() due to missing write permission.

        3. Locking error in wait_if_global_read_lock() due to lock conflict.

  @note In all these cases we have already set the lock type into the lock

        data of the open table(s). If the table(s) are in the open table

        cache, they could be reused with the non-zero lock type set. This

        could lead to ignoring a different lock type with the next lock.

  @note Clear the lock type of all lock data. This ensures that the next

        lock request will set its lock type properly.

*/

static void reset_lock_data_and_free(DrizzleLock*& lock)

{

  lock->reset();

  delete lock;

  lock= NULL;

}

DrizzleLock *Session::lockTables(Table **tables, uint32_t count, uint32_t flags)

{

  DrizzleLock *sql_lock;

  Table *write_lock_used;

  vector<plugin::StorageEngine *> involved_engines;

  do

  {

    if (! (sql_lock= get_lock_data(tables, count, true, &write_lock_used)))

      break;

    if (global_read_lock && write_lock_used and (not (flags & DRIZZLE_LOCK_IGNORE_GLOBAL_READ_LOCK)))

    {

      /*

	Someone has issued LOCK ALL TABLES FOR READ and we want a write lock

	Wait until the lock is gone

      */

      if (wait_if_global_read_lock(1, 1))

      {

        /* Clear the lock type of all lock data to avoid reusage. */

        reset_lock_data_and_free(sql_lock);

	break;

      }

      if (open_tables.version != g_refresh_version)

      {

        /* Clear the lock type of all lock data to avoid reusage. */

        reset_lock_data_and_free(sql_lock);

	break;

      }

    }

    set_proc_info("Notify start statement");

    /*

     * Here, we advise all storage engines involved in the

     * statement that we are starting a new statement

     */

    if (sql_lock->sizeTable())

    {

      size_t num_tables= sql_lock->sizeTable();

      plugin::StorageEngine *engine;

      std::set<size_t> involved_slots;

      for (size_t x= 1; x <= num_tables; x++, tables++)

      {

        engine= (*tables)->cursor->getEngine();

        if (involved_slots.count(engine->getId()) > 0)

          continue; /* already added to involved engines */

        involved_engines.push_back(engine);

        involved_slots.insert(engine->getId());

      }

      for_each(involved_engines.begin(),

               involved_engines.end(),

               bind2nd(mem_fun(&plugin::StorageEngine::startStatement), this));

    }

    set_proc_info("External lock");

    /*

     * Here, the call to lock_external() informs the

     * all engines for all tables used in this statement

     * of the type of lock that Drizzle intends to take on a 

     * specific table.

     */

    if (sql_lock->sizeTable() && lock_external(sql_lock->getTable(), sql_lock->sizeTable()))

    {

      /* Clear the lock type of all lock data to avoid reusage. */

      reset_lock_data_and_free(sql_lock);

      break;

    }

    set_proc_info("Table lock");

    /* Copy the lock data array. thr_multi_lock() reorders its contens. */

    memcpy(sql_lock->getLocks() + sql_lock->sizeLock(),

           sql_lock->getLocks(),

           sql_lock->sizeLock() * sizeof(*sql_lock->getLocks()));

    /* Lock on the copied half of the lock data array. */

    drizzled::error_t rc;

    rc= thr_lock_errno_to_mysql[(int) thr_multi_lock(*this,

                                                     sql_lock->getLocks() +

                                                     sql_lock->sizeLock(),

                                                     sql_lock->sizeLock(),

                                                     this->lock_id)];

    if (rc)                                 /* a timeout or a deadlock */

    {

      if (sql_lock->sizeTable())

        unlock_external(sql_lock->getTable(), sql_lock->sizeTable());

      reset_lock_data_and_free(sql_lock);

      my_error(rc, MYF(0));

    }

  } while(0);

  set_proc_info(0);

  if (getKilled())

  {

    send_kill_message();

    if (sql_lock)

    {

      unlockTables(sql_lock);

      sql_lock= NULL;

    }

  }

  times.set_time_after_lock();

  return sql_lock;

}

int Session::lock_external(Table **tables, uint32_t count)

{

  int lock_type,error;

  for (uint32_t i= 1 ; i <= count ; i++, tables++)

  {

    assert((*tables)->reginfo.lock_type >= TL_READ);

    lock_type=F_WRLCK;				/* Lock exclusive */

    if ((*tables)->db_stat & HA_READ_ONLY ||

      ((*tables)->reginfo.lock_type >= TL_READ &&

      (*tables)->reginfo.lock_type <= TL_READ_NO_INSERT))

      lock_type=F_RDLCK;

    if ((error=(*tables)->cursor->ha_external_lock(this,lock_type)))

    {

      print_lock_error(error, (*tables)->cursor->getEngine()->getName().c_str());

      while (--i)

      {

        tables--;

        (*tables)->cursor->ha_external_lock(this, F_UNLCK);

        (*tables)->current_lock=F_UNLCK;

      }

      return error;

    }

    else

    {

      (*tables)->db_stat &= ~ HA_BLOCK_LOCK;

      (*tables)->current_lock= lock_type;

    }

  }

  return 0;

}

void Session::unlockTables(DrizzleLock *sql_lock)

{

  if (sql_lock->sizeLock())

    sql_lock->unlock(sql_lock->sizeLock());

  if (sql_lock->sizeTable())

    unlock_external(sql_lock->getTable(), sql_lock->sizeTable());

  delete sql_lock;

}

/**

  Unlock some of the tables locked by lockTables.

  This will work even if get_lock_data fails (next unlock will free all)

*/

void Session::unlockSomeTables(Table **table, uint32_t count)

{

  DrizzleLock *sql_lock;

  Table *write_lock_used;

  if ((sql_lock= get_lock_data(table, count, false,

                               &write_lock_used)))

    unlockTables(sql_lock);

}

/**

  unlock all tables locked for read.

*/

void Session::unlockReadTables(DrizzleLock *sql_lock)

{

  uint32_t i,found;

  /* Move all write locks first */

  THR_LOCK_DATA **lock_local= sql_lock->getLocks();

  for (i=found=0 ; i < sql_lock->sizeLock(); i++)

  {

    if (sql_lock->getLocks()[i]->type >= TL_WRITE_ALLOW_READ)

    {

      std::swap(*lock_local, sql_lock->getLocks()[i]);

      lock_local++;

      found++;

    }

  }

  /* unlock the read locked tables */

  if (i != found)

  {

    thr_multi_unlock(lock_local, i - found);

    sql_lock->setLock(found);

  }

  /* Then do the same for the external locks */

  /* Move all write locked tables first */

  Table **table= sql_lock->getTable();

  for (i=found=0 ; i < sql_lock->sizeTable() ; i++)

  {

    assert(sql_lock->getTable()[i]->lock_position == i);

    if ((uint32_t) sql_lock->getTable()[i]->reginfo.lock_type >= TL_WRITE_ALLOW_READ)

    {

      std::swap(*table, sql_lock->getTable()[i]);

      table++;

      found++;

    }

  }

  /* Unlock all read locked tables */

  if (i != found)

  {

    unlock_external(table, i - found);

    sql_lock->resizeTable(found);

  }

  /* Fix the lock positions in Table */

  table= sql_lock->getTable();

  found= 0;

  for (i= 0; i < sql_lock->sizeTable(); i++)

  {

    Table *tbl= *table;

    tbl->lock_position= table - sql_lock->getTable();

    tbl->lock_data_start= found;

    found+= tbl->lock_count;

    table++;

  }

}

/**

  Try to find the table in the list of locked tables.

  In case of success, unlock the table and remove it from this list.

  @note This function has a legacy side effect: the table is

  unlocked even if it is not found in the locked list.

  It's not clear if this side effect is intentional or still

  desirable. It might lead to unmatched calls to

  unlock_external(). Moreover, a discrepancy can be left

  unnoticed by the storage engine, because in

  unlock_external() we call handler::external_lock(F_UNLCK) only

  if table->current_lock is not F_UNLCK.

  @param  session             thread context

  @param  locked          list of locked tables

  @param  table           the table to unlock

  @param  always_unlock   specify explicitly if the legacy side

                          effect is desired.

*/

void Session::removeLock(Table *table)

{

  unlockSomeTables(&table, /* table count */ 1);

}

/** Abort all other threads waiting to get lock in table. */

void Session::abortLock(Table *table)

{

  DrizzleLock *locked;

  Table *write_lock_used;

  if ((locked= get_lock_data(&table, 1, false,

                             &write_lock_used)))

  {

    for (uint32_t x= 0; x < locked->sizeLock(); x++)

      locked->getLocks()[x]->lock->abort_locks();

    delete locked;

  }

}

/**

  Abort one thread / table combination.

  @param session	   Thread handler

  @param table	   Table that should be removed from lock queue

  @retval

    0  Table was not locked by another thread

  @retval

    1  Table was locked by at least one other thread

*/

bool Session::abortLockForThread(Table *table)

{

  bool result= false;

  Table* write_lock_used;

  if (DrizzleLock* locked= get_lock_data(&table, 1, false, &write_lock_used))

  {

    for (uint32_t i= 0; i < locked->sizeLock(); i++)

    {

      if (locked->getLocks()[i]->lock->abort_locks_for_thread(table->in_use->thread_id))

        result= true;

    }

    delete locked;

  }

  return result;

}

/** Unlock a set of external. */

int Session::unlock_external(Table **table, uint32_t count)

{

  int error;

  int error_code=0;

  do

  {

    if ((*table)->current_lock != F_UNLCK)

    {

      (*table)->current_lock = F_UNLCK;

      if ((error=(*table)->cursor->ha_external_lock(this, F_UNLCK)))

      {

	error_code=error;

	print_lock_error(error_code, (*table)->cursor->getEngine()->getName().c_str());

      }

    }

    table++;

  } while (--count);

  return error_code;

}

/**

  Get lock structures from table structs and initialize locks.

  @param session		    Thread handler

  @param table_ptr	    Pointer to tables that should be locks

  @param should_lock		    One of:

           - false      : If we should send TL_IGNORE to store lock

           - true       : Store lock info in Table

  @param write_lock_used   Store pointer to last table with WRITE_ALLOW_WRITE

*/

DrizzleLock *Session::get_lock_data(Table **table_ptr, uint32_t count,

                                    bool should_lock, Table **write_lock_used)

{

  uint32_t lock_count;

  THR_LOCK_DATA **locks, **locks_buf, **locks_start;

  Table **to, **table_buf;

  *write_lock_used=0;

  for (uint32_t i= lock_count= 0 ; i < count ; i++)

  {

    Table *t= table_ptr[i];

    if (! (t->getEngine()->check_flag(HTON_BIT_SKIP_STORE_LOCK)))

    {

      lock_count++;

    }

  }

  /*

    Allocating twice the number of pointers for lock data for use in

    thr_mulit_lock(). This function reorders the lock data, but cannot

    update the table values. So the second part of the array is copied

    from the first part immediately before calling thr_multi_lock().

  */

  DrizzleLock *sql_lock= new DrizzleLock(lock_count);

  if (not sql_lock)

    return NULL;

  locks= locks_buf= sql_lock->getLocks();

  to= table_buf= sql_lock->getTable();

  for (uint32_t i= 0; i < count ; i++)

  {

    Table *table;

    thr_lock_type lock_type;

    if (table_ptr[i]->getEngine()->check_flag(HTON_BIT_SKIP_STORE_LOCK))

      continue;

    table= table_ptr[i];

    lock_type= table->reginfo.lock_type;

    assert (lock_type != TL_WRITE_DEFAULT);

    if (lock_type >= TL_WRITE_ALLOW_WRITE)

    {

      *write_lock_used=table;

      if (table->db_stat & HA_READ_ONLY)

      {

	my_error(ER_OPEN_AS_READONLY, MYF(0), table->getAlias());

        /* Clear the lock type of the lock data that are stored already. */

        sql_lock->setLock(locks - sql_lock->getLocks());

        reset_lock_data_and_free(sql_lock);

	return NULL;

      }

    }

    locks_start= locks;

    locks= table->cursor->store_lock(this, locks, should_lock ? lock_type : TL_IGNORE);

    if (should_lock)

    {

      table->lock_position=   (uint32_t) (to - table_buf);

      table->lock_data_start= (uint32_t) (locks_start - locks_buf);

      table->lock_count=      (uint32_t) (locks - locks_start);

      assert(table->lock_count == 1);

    }

    *to++= table;

  }

  /*

    We do not use 'tables', because there are cases where store_lock()

    returns less locks than lock_count() claimed. This can happen when

    a FLUSH TABLES tries to abort locks from a MERGE table of another

    thread. When that thread has just opened the table, but not yet

    attached its children, it cannot return the locks. lock_count()

    always returns the number of locks that an attached table has.

    This is done to avoid the reverse situation: If lock_count() would

    return 0 for a non-attached MERGE table, and that table becomes

    attached between the calls to lock_count() and store_lock(), then

    we would have allocated too little memory for the lock data. Now

    we may allocate too much, but better safe than memory overrun.

    And in the FLUSH case, the memory is released quickly anyway.

  */

  sql_lock->setLock(locks - locks_buf);

  return sql_lock;

}

/**

  Put a not open table with an old refresh version in the table cache.

  @param table_list		Lock first table in this list

  @param check_in_use           Do we need to check if table already in use by us

  @note

    One must have a lock on table::Cache::mutex()!

  @warning

    If you are going to update the table, you should use

    lock_and_wait_for_table_name(removed) instead of this function as this works

    together with 'FLUSH TABLES WITH READ LOCK'

  @note

    This will force any other threads that uses the table to release it

    as soon as possible.

  @return

    < 0 error

  @return

    == 0 table locked

  @return

    > 0  table locked, but someone is using it

*/

int Session::lock_table_name(TableList *table_list)

{

  identifier::Table identifier(table_list->getSchemaName(), table_list->getTableName());

  {

    /* Only insert the table if we haven't insert it already */

    table::CacheRange ppp= table::getCache().equal_range(identifier.getKey());

    for (table::CacheMap::const_iterator iter= ppp.first; iter != ppp.second; ++iter)

    {

      Table *table= iter->second;

      if (table->reginfo.lock_type < TL_WRITE)

        continue;

      if (table->in_use == this)

      {

        table->getMutableShare()->resetVersion();                  // Ensure no one can use this

        table->locked_by_name= true;

        return 0;

      }

    }

  }

  table::Placeholder *table= &table_cache_insert_placeholder(identifier);

  table_list->table= reinterpret_cast<Table*>(table);

  /* Return 1 if table is in use */

  return (test(table::Cache::removeTable(*this, identifier, RTFC_NO_FLAG)));

}

void TableList::unlock_table_name()

{

  if (table)

  {

    table::remove_table(static_cast<table::Concurrent *>(table));

    locking::broadcast_refresh();

  }

}

static bool locked_named_table(TableList *table_list)

{

  for (; table_list; table_list=table_list->next_local)

  {

    Table *table= table_list->table;

    if (table)

    {

      Table *save_next= table->getNext();

      table->setNext(NULL);

      bool result= table::Cache::areTablesUsed(table_list->table, 0);

      table->setNext(save_next);

      if (result)

        return 1;

    }

  }

  return 0;					// All tables are locked

}

bool Session::wait_for_locked_table_names(TableList *table_list)

{

  bool result= false;

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