~drizzle-trunk/drizzle/development

/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-

 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:

 *

 *  Copyright (C) 2009 Sun Microsystems

 *

 *  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; either version 2 of the License, or

 *  (at your option) any later version.

 *

 *  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

 */

/*

  This class is shared between different table objects. There is one

  instance of table share per one table in the database.

*/

/* Basic functions needed by many modules */

#include <drizzled/server_includes.h>

#include <assert.h>

#include <drizzled/error.h>

#include <drizzled/gettext.h>

#include <drizzled/sql_base.h>

using namespace std;

static HASH table_def_cache;

static pthread_mutex_t LOCK_table_share;

bool table_def_inited= false;

/*****************************************************************************

  Functions to handle table definition cach (TableShare)

 *****************************************************************************/

extern "C"

{

  unsigned char *table_def_key(const unsigned char *record,

                               size_t *length,

                               bool );

}

unsigned char *table_def_key(const unsigned char *record,

                             size_t *length,

                             bool )

{

  TableShare *entry=(TableShare*) record;

  *length= entry->table_cache_key.length;

  return (unsigned char*) entry->table_cache_key.str;

}

static void table_def_free_entry(TableShare *share)

{

  share->free_table_share();

}

bool TableShare::cacheStart(void)

{

  table_def_inited= true;

  pthread_mutex_init(&LOCK_table_share, MY_MUTEX_INIT_FAST);

  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 TableShare::cacheStop(void)

{

  if (table_def_inited)

  {

    table_def_inited= 0;

    pthread_mutex_destroy(&LOCK_table_share);

    hash_free(&table_def_cache);

  }

}

uint32_t cached_table_definitions(void)

{

  return table_def_cache.records;

}

/*

  Mark that we are not using table share anymore.

  SYNOPSIS

  release()

  share		Table share

  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.

*/

void TableShare::release(TableShare *share)

{

  bool to_be_deleted= false;

  safe_mutex_assert_owner(&LOCK_open);

  pthread_mutex_lock(&share->mutex);

  if (!--share->ref_count)

    to_be_deleted= true;

  if (to_be_deleted)

  {

    hash_delete(&table_def_cache, (unsigned char*) share);

    return;

  }

  pthread_mutex_unlock(&share->mutex);

}

void TableShare::release(const char *key, uint32_t key_length)

{

  TableShare *share;

  if ((share= (TableShare*) 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);

    }

  }

}

/*

  Get TableShare 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

  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

*/

TableShare *TableShare::getShare(Session *session, 

                                 TableList *table_list, char *key,

                                 uint32_t key_length, uint32_t, int *error)

{

  TableShare *share;

  *error= 0;

  /* Read table definition from cache */

  if ((share= (TableShare*) hash_search(&table_def_cache,(unsigned char*) key,

                                        key_length)))

    goto found;

  if (!(share= alloc_table_share(table_list, key, key_length)))

  {

    return NULL;

  }

  /*

    Lock mutex to be able to read table definition from file without

    conflicts

  */

  (void) pthread_mutex_lock(&share->mutex);

  if (my_hash_insert(&table_def_cache, (unsigned char*) share))

  {

    share->free_table_share();

    return NULL;				// return error

  }

  if (open_table_def(session, share))

  {

    *error= share->error;

    (void) hash_delete(&table_def_cache, (unsigned char*) share);

    return NULL;

  }

  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 */

    share->open_table_error(share->error, share->open_errno, share->errarg);

    (void) pthread_mutex_unlock(&share->mutex);

    return NULL;

  }

  share->ref_count++;

  (void) pthread_mutex_unlock(&share->mutex);

  return share;

}

/*

  Check if table definition exits in cache

  SYNOPSIS

  get_cached_table_share()

  db			Database name

  table_name		Table name

  RETURN

  0  Not cached

#  TableShare for table

*/

TableShare *TableShare::getShare(const char *db, const char *table_name)

{

  char key[NAME_LEN*2+2];

  uint32_t key_length;

  safe_mutex_assert_owner(&LOCK_open);

  key_length= TableShare::createKey(key, db, table_name);

  return (TableShare*) hash_search(&table_def_cache,(unsigned char*) key, key_length);

}