~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 "config.h"

#include <pthread.h>

#include <cassert>

#include "drizzled/error.h"

#include "drizzled/gettext.h"

#include "drizzled/sql_base.h"

#include "drizzled/hash.h"

#include "drizzled/pthread_globals.h"

#include "drizzled/internal/my_pthread.h"

using namespace std;

extern size_t table_def_size;

typedef drizzled::hash_map<string, TableShare *> TableDefCache;

TableDefCache table_def_cache;

static pthread_mutex_t LOCK_table_share;

bool table_def_inited= false;

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

  Functions to handle table definition cach (TableShare)

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

void TableShare::cacheStart(void)

{

  pthread_mutex_init(&LOCK_table_share, MY_MUTEX_INIT_FAST);

  table_def_inited= true;

  /* 

   * This is going to overalloc a bit - as rehash sets the number of

   * buckets, not the number of elements. BUT, it'll allow us to not need

   * to rehash later on as the hash_map grows.

   */

  table_def_cache.rehash(table_def_size);

}

void TableShare::cacheStop(void)

{

  if (table_def_inited)

  {

    table_def_inited= false;

    pthread_mutex_destroy(&LOCK_table_share);

  }

}

/**

 * @TODO: This should return size_t

 */

uint32_t cached_table_definitions(void)

{

  return static_cast<uint32_t>(table_def_cache.size());

}

/*

  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)

  {

    const string key_string(share->table_cache_key.str,

                            share->table_cache_key.length);

    TableDefCache::iterator iter= table_def_cache.find(key_string);

    if (iter != table_def_cache.end())

    {

      (*iter).second->free_table_share();

      table_def_cache.erase(iter);

    }

    return;

  }

  pthread_mutex_unlock(&share->mutex);

}

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

{

  const string key_string(key, key_length);

  TableDefCache::iterator iter= table_def_cache.find(key_string);

  if (iter != table_def_cache.end())

  {

    TableShare *share= (*iter).second;

    share->version= 0;                          // Mark for delete

    if (share->ref_count == 0)

    {

      pthread_mutex_lock(&share->mutex);

      share->free_table_share();

      table_def_cache.erase(key_string);

    }

  }

}

static TableShare *foundTableShare(TableShare *share)

{

  /*

    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;

}

/*

  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)

{

  const string key_string(key, key_length);

  TableShare *share= NULL;

  *error= 0;

  /* Read table definition from cache */

  TableDefCache::iterator iter= table_def_cache.find(key_string);

  if (iter != table_def_cache.end())

  {

    share= (*iter).second;

    return foundTableShare(share);

  }

  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);

  /**

   * @TODO: we need to eject something if we exceed table_def_size

   */

  pair<TableDefCache::iterator, bool> ret=

    table_def_cache.insert(make_pair(key_string, share));

  if (ret.second == false)

  {

    share->free_table_share();

    return NULL;

  }

  if (open_table_def(*session, share))

  {

    *error= share->error;

    table_def_cache.erase(key_string);

    share->free_table_share();

    return NULL;

  }

  share->ref_count++;				// Mark in use

  (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);

  const string key_string(key, key_length);

  TableDefCache::iterator iter= table_def_cache.find(key_string);

  if (iter != table_def_cache.end())

  {

    return (*iter).second;

  }

  else

  {

    return NULL;

  }

}