~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);
}