path: root/sql/handler.cc

/* 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 */


/* Handler-calling-functions */

#ifdef USE_PRAGMA_IMPLEMENTATION
#pragma implementation				// gcc: Class implementation
#endif

#include "mysql_priv.h"
#include "ha_heap.h"
#include "ha_myisam.h"
#include "ha_myisammrg.h"


/*
  We have dummy hanldertons in case the handler has not been compiled
  in. This will be removed in 5.1.
*/
#ifdef HAVE_BERKELEY_DB
#include "ha_berkeley.h"
extern handlerton berkeley_hton;
#else
handlerton berkeley_hton = { "BerkeleyDB", SHOW_OPTION_NO,
  "Supports transactions and page-level locking", DB_TYPE_BERKELEY_DB, NULL,
  0, 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
  NULL, NULL, HTON_NO_FLAGS };
#endif
#ifdef HAVE_BLACKHOLE_DB
#include "ha_blackhole.h"
extern handlerton blackhole_hton;
#else
handlerton blackhole_hton = { "BLACKHOLE", SHOW_OPTION_NO,
  "/dev/null storage engine (anything you write to it disappears)",
  DB_TYPE_BLACKHOLE_DB, NULL, 0, 0, NULL, NULL,
  NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
  HTON_NO_FLAGS };
#endif
#ifdef HAVE_EXAMPLE_DB
#include "examples/ha_example.h"
extern handlerton example_hton;
#else
handlerton example_hton = { "EXAMPLE", SHOW_OPTION_NO,
  "Example storage engine",
  DB_TYPE_EXAMPLE_DB, NULL, 0, 0, NULL, NULL,
  NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
  HTON_NO_FLAGS };
#endif
#if defined(HAVE_ARCHIVE_DB)
#include "ha_archive.h"
extern handlerton archive_hton;
#else
handlerton archive_hton = { "ARCHIVE", SHOW_OPTION_NO,
  "Archive storage engine", DB_TYPE_ARCHIVE_DB, NULL, 0, 0, NULL, NULL,
  NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
  HTON_NO_FLAGS };
#endif
#ifdef HAVE_CSV_DB
#include "examples/ha_tina.h"
extern handlerton tina_hton;
#else
handlerton tina_hton = { "CSV", SHOW_OPTION_NO, "CSV storage engine",
  DB_TYPE_CSV_DB, NULL, 0, 0, NULL, NULL,
  NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
  HTON_NO_FLAGS };
#endif
#ifdef HAVE_INNOBASE_DB
#include "ha_innodb.h"
extern handlerton innobase_hton;
#else
handlerton innobase_hton = { "InnoDB", SHOW_OPTION_NO,
  "Supports transactions, row-level locking, and foreign keys",
  DB_TYPE_INNODB, NULL, 0, 0, NULL, NULL,
  NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
  HTON_NO_FLAGS };
#endif
#ifdef HAVE_NDBCLUSTER_DB
#include "ha_ndbcluster.h"
extern handlerton ndbcluster_hton;
#else
handlerton ndbcluster_hton = { "ndbcluster", SHOW_OPTION_NO,
  "Clustered, fault-tolerant, memory-based tables",
  DB_TYPE_NDBCLUSTER, NULL, 0, 0, NULL, NULL,
  NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
  HTON_NO_FLAGS };
#endif
#ifdef HAVE_FEDERATED_DB
#include "ha_federated.h"
extern handlerton federated_hton;
#else
handlerton federated_hton = { "FEDERATED", SHOW_OPTION_NO,
  "Federated MySQL storage engine", DB_TYPE_FEDERATED_DB, NULL, 0, 0, NULL,
  NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
  HTON_NO_FLAGS };
#endif
#include <myisampack.h>
#include <errno.h>

extern handlerton myisam_hton;
extern handlerton myisammrg_hton;
extern handlerton heap_hton;
extern handlerton binlog_hton;

/*
  Obsolete
*/
handlerton isam_hton = { "ISAM", SHOW_OPTION_NO, "Obsolete storage engine",
  DB_TYPE_ISAM, NULL, 0, 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
  NULL, NULL, NULL, NULL, NULL, NULL, HTON_NO_FLAGS };

/* number of entries in handlertons[] */
ulong total_ha;
/* number of storage engines (from handlertons[]) that support 2pc */
ulong total_ha_2pc;
/* size of savepoint storage area (see ha_init) */
ulong savepoint_alloc_size;

/*
  This array is used for processing compiled in engines.
*/
handlerton *sys_table_types[]=
{
  &myisam_hton,
  &heap_hton,
  &innobase_hton,
  &berkeley_hton,
  &blackhole_hton,
  &example_hton,
  &archive_hton,
  &tina_hton,
  &ndbcluster_hton,
  &federated_hton,
  &myisammrg_hton,
  &binlog_hton,
  &isam_hton,
  NULL
};

struct show_table_alias_st sys_table_aliases[]=
{
  {"INNOBASE",	"InnoDB"},
  {"NDB", "NDBCLUSTER"},
  {"BDB", "BERKELEYDB"},
  {"HEAP", "MEMORY"},
  {"MERGE", "MRG_MYISAM"},
  {NullS, NullS}
};

const char *ha_row_type[] = {
  "", "FIXED", "DYNAMIC", "COMPRESSED", "REDUNDANT", "COMPACT", "?","?","?"
};

const char *tx_isolation_names[] =
{ "READ-UNCOMMITTED", "READ-COMMITTED", "REPEATABLE-READ", "SERIALIZABLE",
  NullS};
TYPELIB tx_isolation_typelib= {array_elements(tx_isolation_names)-1,"",
			       tx_isolation_names, NULL};

static TYPELIB known_extensions= {0,"known_exts", NULL, NULL};
uint known_extensions_id= 0;

enum db_type ha_resolve_by_name(const char *name, uint namelen)
{
  THD *thd= current_thd;
  show_table_alias_st *table_alias;
  handlerton **types;

  if (thd && !my_strnncoll(&my_charset_latin1,
                           (const uchar *)name, namelen,
                           (const uchar *)"DEFAULT", 7))
    return (enum db_type) thd->variables.table_type;

retest:
  for (types= sys_table_types; *types; types++)
  {
    if (!my_strnncoll(&my_charset_latin1,
                      (const uchar *)name, namelen,
                      (const uchar *)(*types)->name, 
                      (uint) strlen((*types)->name)))
      return (enum db_type) (*types)->db_type;
  }

  /*
    We check for the historical aliases.
  */
  for (table_alias= sys_table_aliases; table_alias->type; table_alias++)
  {
    if (!my_strnncoll(&my_charset_latin1,
                      (const uchar *)name, namelen,
                      (const uchar *)table_alias->alias,
                      (uint) strlen(table_alias->alias)))
    {
      name= table_alias->type;
      namelen= (uint) strlen(name);
      goto retest;
    }
  }

  return DB_TYPE_UNKNOWN;
}


const char *ha_get_storage_engine(enum db_type db_type)
{
  handlerton **types;
  for (types= sys_table_types; *types; types++)
  {
    if (db_type == (*types)->db_type)
      return (*types)->name;
  }
  return "*NONE*";
}


bool ha_check_storage_engine_flag(enum db_type db_type, uint32 flag)
{
  handlerton **types;
  for (types= sys_table_types; *types; types++)
  {
    if (db_type == (*types)->db_type)
      return test((*types)->flags & flag);
  }
  return FALSE;                                 // No matching engine
}


my_bool ha_storage_engine_is_enabled(enum db_type database_type)
{
  handlerton **types;
  for (types= sys_table_types; *types; types++)
  {
    if ((database_type == (*types)->db_type) &&
	((*types)->state == SHOW_OPTION_YES))
      return TRUE;
  }
  return FALSE;
}


/* Use other database handler if databasehandler is not compiled in */

enum db_type ha_checktype(THD *thd, enum db_type database_type,
                          bool no_substitute, bool report_error)
{
  if (ha_storage_engine_is_enabled(database_type))
    return database_type;

  if (no_substitute)
  {
    if (report_error)
    {
      const char *engine_name= ha_get_storage_engine(database_type);
      my_error(ER_FEATURE_DISABLED,MYF(0),engine_name,engine_name);
    }
    return DB_TYPE_UNKNOWN;
  }

  switch (database_type) {
#ifndef NO_HASH
  case DB_TYPE_HASH:
    return (database_type);
#endif
  case DB_TYPE_MRG_ISAM:
    return (DB_TYPE_MRG_MYISAM);
  default:
    break;
  }

  return ((enum db_type) thd->variables.table_type != DB_TYPE_UNKNOWN ?
          (enum db_type) thd->variables.table_type :
          ((enum db_type) global_system_variables.table_type !=
           DB_TYPE_UNKNOWN ?
           (enum db_type) global_system_variables.table_type : DB_TYPE_MYISAM)
          );
} /* ha_checktype */


handler *get_new_handler(TABLE *table, MEM_ROOT *alloc, enum db_type db_type)
{
  switch (db_type) {
#ifndef NO_HASH
  case DB_TYPE_HASH:
    return new (alloc) ha_hash(table);
#endif
  case DB_TYPE_MRG_MYISAM:
  case DB_TYPE_MRG_ISAM:
    if (have_merge_db == SHOW_OPTION_YES)
      return new (alloc) ha_myisammrg(table);
    return NULL;
#ifdef HAVE_BERKELEY_DB
  case DB_TYPE_BERKELEY_DB:
    if (have_berkeley_db == SHOW_OPTION_YES)
      return new (alloc) ha_berkeley(table);
    return NULL;
#endif
#ifdef HAVE_INNOBASE_DB
  case DB_TYPE_INNODB:
    if (have_innodb == SHOW_OPTION_YES)
      return new (alloc) ha_innobase(table);
    return NULL;
#endif
#ifdef HAVE_EXAMPLE_DB
  case DB_TYPE_EXAMPLE_DB:
    if (have_example_db == SHOW_OPTION_YES)
      return new (alloc) ha_example(table);
    return NULL;
#endif
#if defined(HAVE_ARCHIVE_DB)
  case DB_TYPE_ARCHIVE_DB:
    if (have_archive_db == SHOW_OPTION_YES)
      return new (alloc) ha_archive(table);
    return NULL;
#endif
#ifdef HAVE_BLACKHOLE_DB
  case DB_TYPE_BLACKHOLE_DB:
    if (have_blackhole_db == SHOW_OPTION_YES)
      return new (alloc) ha_blackhole(table);
    return NULL;
#endif
#ifdef HAVE_FEDERATED_DB
  case DB_TYPE_FEDERATED_DB:
    if (have_federated_db == SHOW_OPTION_YES)
      return new (alloc) ha_federated(table);
    return NULL;
#endif
#ifdef HAVE_CSV_DB
  case DB_TYPE_CSV_DB:
    if (have_csv_db == SHOW_OPTION_YES)
      return new (alloc) ha_tina(table);
    return NULL;
#endif
#ifdef HAVE_NDBCLUSTER_DB
  case DB_TYPE_NDBCLUSTER:
    if (have_ndbcluster == SHOW_OPTION_YES)
      return new (alloc) ha_ndbcluster(table);
    return NULL;
#endif
  case DB_TYPE_HEAP:
    return new (alloc) ha_heap(table);
  default:					// should never happen
  {
    enum db_type def=(enum db_type) current_thd->variables.table_type;
    /* Try first with 'default table type' */
    if (db_type != def)
      return get_new_handler(table, alloc, def);
  }
  /* Fall back to MyISAM */
  case DB_TYPE_MYISAM:
    return new (alloc) ha_myisam(table);
  }
}

/*
  Register handler error messages for use with my_error().

  SYNOPSIS
    ha_init_errors()

  RETURN
    0           OK
    != 0        Error
*/

static int ha_init_errors(void)
{
#define SETMSG(nr, msg) errmsgs[(nr) - HA_ERR_FIRST]= (msg)
  const char    **errmsgs;

  /* Allocate a pointer array for the error message strings. */
  /* Zerofill it to avoid uninitialized gaps. */
  if (! (errmsgs= (const char**) my_malloc(HA_ERR_ERRORS * sizeof(char*),
                                           MYF(MY_WME | MY_ZEROFILL))))
    return 1;

  /* Set the dedicated error messages. */
  SETMSG(HA_ERR_KEY_NOT_FOUND,          ER(ER_KEY_NOT_FOUND));
  SETMSG(HA_ERR_FOUND_DUPP_KEY,         ER(ER_DUP_KEY));
  SETMSG(HA_ERR_RECORD_CHANGED,         "Update wich is recoverable");
  SETMSG(HA_ERR_WRONG_INDEX,            "Wrong index given to function");
  SETMSG(HA_ERR_CRASHED,                ER(ER_NOT_KEYFILE));
  SETMSG(HA_ERR_WRONG_IN_RECORD,        ER(ER_CRASHED_ON_USAGE));
  SETMSG(HA_ERR_OUT_OF_MEM,             "Table handler out of memory");
  SETMSG(HA_ERR_NOT_A_TABLE,            "Incorrect file format '%.64s'");
  SETMSG(HA_ERR_WRONG_COMMAND,          "Command not supported");
  SETMSG(HA_ERR_OLD_FILE,               ER(ER_OLD_KEYFILE));
  SETMSG(HA_ERR_NO_ACTIVE_RECORD,       "No record read in update");
  SETMSG(HA_ERR_RECORD_DELETED,         "Intern record deleted");
  SETMSG(HA_ERR_RECORD_FILE_FULL,       ER(ER_RECORD_FILE_FULL));
  SETMSG(HA_ERR_INDEX_FILE_FULL,        "No more room in index file '%.64s'");
  SETMSG(HA_ERR_END_OF_FILE,            "End in next/prev/first/last");
  SETMSG(HA_ERR_UNSUPPORTED,            ER(ER_ILLEGAL_HA));
  SETMSG(HA_ERR_TO_BIG_ROW,             "Too big row");
  SETMSG(HA_WRONG_CREATE_OPTION,        "Wrong create option");
  SETMSG(HA_ERR_FOUND_DUPP_UNIQUE,      ER(ER_DUP_UNIQUE));
  SETMSG(HA_ERR_UNKNOWN_CHARSET,        "Can't open charset");
  SETMSG(HA_ERR_WRONG_MRG_TABLE_DEF,    ER(ER_WRONG_MRG_TABLE));
  SETMSG(HA_ERR_CRASHED_ON_REPAIR,      ER(ER_CRASHED_ON_REPAIR));
  SETMSG(HA_ERR_CRASHED_ON_USAGE,       ER(ER_CRASHED_ON_USAGE));
  SETMSG(HA_ERR_LOCK_WAIT_TIMEOUT,      ER(ER_LOCK_WAIT_TIMEOUT));
  SETMSG(HA_ERR_LOCK_TABLE_FULL,        ER(ER_LOCK_TABLE_FULL));
  SETMSG(HA_ERR_READ_ONLY_TRANSACTION,  ER(ER_READ_ONLY_TRANSACTION));
  SETMSG(HA_ERR_LOCK_DEADLOCK,          ER(ER_LOCK_DEADLOCK));
  SETMSG(HA_ERR_CANNOT_ADD_FOREIGN,     ER(ER_CANNOT_ADD_FOREIGN));
  SETMSG(HA_ERR_NO_REFERENCED_ROW,      ER(ER_NO_REFERENCED_ROW_2));
  SETMSG(HA_ERR_ROW_IS_REFERENCED,      ER(ER_ROW_IS_REFERENCED_2));
  SETMSG(HA_ERR_NO_SAVEPOINT,           "No savepoint with that name");
  SETMSG(HA_ERR_NON_UNIQUE_BLOCK_SIZE,  "Non unique key block size");
  SETMSG(HA_ERR_NO_SUCH_TABLE,          "No such table: '%.64s'");
  SETMSG(HA_ERR_TABLE_EXIST,            ER(ER_TABLE_EXISTS_ERROR));
  SETMSG(HA_ERR_NO_CONNECTION,          "Could not connect to storage engine");
  SETMSG(HA_ERR_TABLE_DEF_CHANGED,      ER(ER_TABLE_DEF_CHANGED));
  SETMSG(HA_ERR_TABLE_NEEDS_UPGRADE,    ER(ER_TABLE_NEEDS_UPGRADE));
  SETMSG(HA_ERR_TABLE_READONLY,         ER(ER_OPEN_AS_READONLY));
  SETMSG(HA_ERR_AUTOINC_READ_FAILED,    ER(ER_AUTOINC_READ_FAILED));
  SETMSG(HA_ERR_AUTOINC_ERANGE,         ER(ER_WARN_DATA_OUT_OF_RANGE));
  SETMSG(HA_ERR_TOO_MANY_CONCURRENT_TRXS, ER(ER_TOO_MANY_CONCURRENT_TRXS));

  /* Register the error messages for use with my_error(). */
  return my_error_register(errmsgs, HA_ERR_FIRST, HA_ERR_LAST);
}


/*
  Unregister handler error messages.

  SYNOPSIS
    ha_finish_errors()

  RETURN
    0           OK
    != 0        Error
*/

static int ha_finish_errors(void)
{
  const char    **errmsgs;

  /* Allocate a pointer array for the error message strings. */
  if (! (errmsgs= my_error_unregister(HA_ERR_FIRST, HA_ERR_LAST)))
    return 1;
  my_free((gptr) errmsgs, MYF(0));
  return 0;
}


static inline void ha_was_inited_ok(handlerton **ht)
{
  uint tmp= (*ht)->savepoint_offset;
  (*ht)->savepoint_offset= savepoint_alloc_size;
  savepoint_alloc_size+= tmp;
  (*ht)->slot= total_ha++;
  if ((*ht)->prepare)
    total_ha_2pc++;
}

int ha_init()
{
  int error= 0;
  handlerton **types;
  total_ha= savepoint_alloc_size= 0;

  if (ha_init_errors())
    return 1;

  /*
    We now initialize everything here.
  */
  for (types= sys_table_types; *types; types++)
  {
    if (!(*types)->init || !(*types)->init())
      ha_was_inited_ok(types);
    else
      (*types)->state= SHOW_OPTION_DISABLED;
  }

  DBUG_ASSERT(total_ha < MAX_HA);
  /*
    Check if there is a transaction-capable storage engine besides the
    binary log (which is considered a transaction-capable storage engine in
    counting total_ha)
  */
  opt_using_transactions= total_ha>(ulong)opt_bin_log;
  savepoint_alloc_size+= sizeof(SAVEPOINT);
  return error;
}

	/* close, flush or restart databases */
	/* Ignore this for other databases than ours */

int ha_panic(enum ha_panic_function flag)
{
  int error=0;
#ifndef NO_HASH
  error|=h_panic(flag);			/* fix hash */
#endif
#ifdef HAVE_ISAM
  error|=mrg_panic(flag);
  error|=nisam_panic(flag);
#endif
  error|=heap_panic(flag);
  error|=mi_panic(flag);
  error|=myrg_panic(flag);
#ifdef HAVE_BERKELEY_DB
  if (have_berkeley_db == SHOW_OPTION_YES)
    error|=berkeley_end();
#endif
#ifdef HAVE_BLACKHOLE_DB
  if (have_blackhole_db == SHOW_OPTION_YES)
    error|= blackhole_db_end();
#endif
#ifdef HAVE_INNOBASE_DB
  if (have_innodb == SHOW_OPTION_YES)
    error|=innobase_end();
#endif
#ifdef HAVE_NDBCLUSTER_DB
  if (have_ndbcluster == SHOW_OPTION_YES)
    error|=ndbcluster_end();
#endif
#ifdef HAVE_FEDERATED_DB
  if (have_federated_db == SHOW_OPTION_YES)
    error|= federated_db_end();
#endif
#if defined(HAVE_ARCHIVE_DB)
  if (have_archive_db == SHOW_OPTION_YES)
    error|= archive_db_end();
#endif
#ifdef HAVE_CSV_DB
  if (have_csv_db == SHOW_OPTION_YES)
    error|= tina_end();
#endif
  if (ha_finish_errors())
    error= 1;
  return error;
} /* ha_panic */

void ha_drop_database(char* path)
{
#ifdef HAVE_INNOBASE_DB
  if (have_innodb == SHOW_OPTION_YES)
    innobase_drop_database(path);
#endif
#ifdef HAVE_NDBCLUSTER_DB
  if (have_ndbcluster == SHOW_OPTION_YES)
    ndbcluster_drop_database(path);
#endif
}

/* don't bother to rollback here, it's done already */
void ha_close_connection(THD* thd)
{
  handlerton **types;
  for (types= sys_table_types; *types; types++)
    if (thd->ha_data[(*types)->slot])
      (*types)->close_connection(thd);
}

/* ========================================================================
 ======================= TRANSACTIONS ===================================*/

/*
  Register a storage engine for a transaction

  DESCRIPTION
    Every storage engine MUST call this function when it starts
    a transaction or a statement (that is it must be called both for the
    "beginning of transaction" and "beginning of statement").
    Only storage engines registered for the transaction/statement
    will know when to commit/rollback it.

  NOTE
    trans_register_ha is idempotent - storage engine may register many
    times per transaction.

*/
void trans_register_ha(THD *thd, bool all, handlerton *ht_arg)
{
  THD_TRANS *trans;
  handlerton **ht;
  DBUG_ENTER("trans_register_ha");
  DBUG_PRINT("enter",("%s", all ? "all" : "stmt"));

  if (all)
  {
    trans= &thd->transaction.all;
    thd->server_status|= SERVER_STATUS_IN_TRANS;
  }
  else
    trans= &thd->transaction.stmt;

  for (ht=trans->ht; *ht; ht++)
    if (*ht == ht_arg)
      DBUG_VOID_RETURN;  /* already registered, return */

  trans->ht[trans->nht++]=ht_arg;
  DBUG_ASSERT(*ht == ht_arg);
  trans->no_2pc|=(ht_arg->prepare==0);
  if (thd->transaction.xid_state.xid.is_null())
    thd->transaction.xid_state.xid.set(thd->query_id);
  DBUG_VOID_RETURN;
}

/*
  RETURN
      0  - ok
      1  - error, transaction was rolled back
*/
int ha_prepare(THD *thd)
{
  int error=0, all=1;
  THD_TRANS *trans=all ? &thd->transaction.all : &thd->transaction.stmt;
  handlerton **ht=trans->ht;
  DBUG_ENTER("ha_prepare");
#ifdef USING_TRANSACTIONS
  if (trans->nht)
  {
    for (; *ht; ht++)
    {
      int err;
      statistic_increment(thd->status_var.ha_prepare_count,&LOCK_status);
      if ((*ht)->prepare)
      {
        if ((err= (*(*ht)->prepare)(thd, all)))
        {
          my_error(ER_ERROR_DURING_COMMIT, MYF(0), err);
          ha_rollback_trans(thd, all);
          error=1;
          break;
        }
      }
      else
      {
        push_warning_printf(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
                            ER_ILLEGAL_HA, ER(ER_ILLEGAL_HA), (*ht)->name);
      }
    }
  }
#endif /* USING_TRANSACTIONS */
  DBUG_RETURN(error);
}

/*
  RETURN
      0  - ok
      1  - transaction was rolled back
      2  - error during commit, data may be inconsistent
*/
int ha_commit_trans(THD *thd, bool all)
{
  int error= 0, cookie= 0;
  THD_TRANS *trans= all ? &thd->transaction.all : &thd->transaction.stmt;
  bool is_real_trans= all || thd->transaction.all.nht == 0;
  handlerton **ht= trans->ht;
  my_xid xid= thd->transaction.xid_state.xid.get_my_xid();
  DBUG_ENTER("ha_commit_trans");

  if (thd->in_sub_stmt)
  {
    /*
      Since we don't support nested statement transactions in 5.0,
      we can't commit or rollback stmt transactions while we are inside
      stored functions or triggers. So we simply do nothing now.
      TODO: This should be fixed in later ( >= 5.1) releases.
    */
    if (!all)
      DBUG_RETURN(0);
    /*
      We assume that all statements which commit or rollback main transaction
      are prohibited inside of stored functions or triggers. So they should
      bail out with error even before ha_commit_trans() call. To be 100% safe
      let us throw error in non-debug builds.
    */
    DBUG_ASSERT(0);
    my_error(ER_COMMIT_NOT_ALLOWED_IN_SF_OR_TRG, MYF(0));
    DBUG_RETURN(2);
  }
#ifdef USING_TRANSACTIONS
  if (trans->nht)
  {
    if (is_real_trans && wait_if_global_read_lock(thd, 0, 0))
    {
      ha_rollback_trans(thd, all);
      DBUG_RETURN(1);
    }
    DBUG_EXECUTE_IF("crash_commit_before", abort(););

    /* Close all cursors that can not survive COMMIT */
    if (is_real_trans)                          /* not a statement commit */
      thd->stmt_map.close_transient_cursors();

    if (!trans->no_2pc && trans->nht > 1)
    {
      for (; *ht && !error; ht++)
      {
        int err;
        if ((err= (*(*ht)->prepare)(thd, all)))
        {
          my_error(ER_ERROR_DURING_COMMIT, MYF(0), err);
          error= 1;
        }
        statistic_increment(thd->status_var.ha_prepare_count,&LOCK_status);
      }
      DBUG_EXECUTE_IF("crash_commit_after_prepare", abort(););
      if (error || (is_real_trans && xid &&
                    (error= !(cookie= tc_log->log_xid(thd, xid)))))
      {
        ha_rollback_trans(thd, all);
        error= 1;
        goto end;
      }
      DBUG_EXECUTE_IF("crash_commit_after_log", abort(););
    }
    error=ha_commit_one_phase(thd, all) ? (cookie ? 2 : 1) : 0;
    DBUG_EXECUTE_IF("crash_commit_before_unlog", abort(););
    if (cookie)
      tc_log->unlog(cookie, xid);
    DBUG_EXECUTE_IF("crash_commit_after", abort(););
end:
    if (is_real_trans)
      start_waiting_global_read_lock(thd);
  }
  else if (all)
  {
    /*
      A COMMIT of an empty transaction. There may be savepoints.
      Destroy them. If the transaction is not empty
      savepoints are cleared in ha_commit_one_phase()
      or ha_rollback_trans().
    */
    thd->transaction.cleanup();
  }
#endif /* USING_TRANSACTIONS */
  DBUG_RETURN(error);
}

/*
  NOTE - this function does not care about global read lock.
  A caller should.
*/
int ha_commit_one_phase(THD *thd, bool all)
{
  int error=0;
  THD_TRANS *trans=all ? &thd->transaction.all : &thd->transaction.stmt;
  bool is_real_trans=all || thd->transaction.all.nht == 0;
  handlerton **ht=trans->ht;
  DBUG_ENTER("ha_commit_one_phase");
#ifdef USING_TRANSACTIONS
  if (trans->nht)
  {
    for (ht=trans->ht; *ht; ht++)
    {
      int err;
      if ((err= (*(*ht)->commit)(thd, all)))
      {
        my_error(ER_ERROR_DURING_COMMIT, MYF(0), err);
        error=1;
      }
      statistic_increment(thd->status_var.ha_commit_count,&LOCK_status);
      *ht= 0;
    }
    trans->nht=0;
    trans->no_2pc=0;
    if (is_real_trans)
      thd->transaction.xid_state.xid.null();
    if (all)
    {
#ifdef HAVE_QUERY_CACHE
      if (thd->transaction.changed_tables)
        query_cache.invalidate(thd->transaction.changed_tables);
#endif
      thd->variables.tx_isolation=thd->session_tx_isolation;
      thd->transaction.cleanup();
    }
  }
#endif /* USING_TRANSACTIONS */
  DBUG_RETURN(error);
}


int ha_rollback_trans(THD *thd, bool all)
{
  int error=0;
  THD_TRANS *trans=all ? &thd->transaction.all : &thd->transaction.stmt;
  bool is_real_trans=all || thd->transaction.all.nht == 0;
  DBUG_ENTER("ha_rollback_trans");
  if (thd->in_sub_stmt)
  {
    /*
      If we are inside stored function or trigger we should not commit or
      rollback current statement transaction. See comment in ha_commit_trans()
      call for more information.
    */
    if (!all)
      DBUG_RETURN(0);
    DBUG_ASSERT(0);
    my_error(ER_COMMIT_NOT_ALLOWED_IN_SF_OR_TRG, MYF(0));
    DBUG_RETURN(1);
  }
#ifdef USING_TRANSACTIONS
  if (trans->nht)
  {
    /* Close all cursors that can not survive ROLLBACK */
    if (is_real_trans)                          /* not a statement commit */
      thd->stmt_map.close_transient_cursors();

    for (handlerton **ht=trans->ht; *ht; ht++)
    {
      int err;
      if ((err= (*(*ht)->rollback)(thd, all)))
      { // cannot happen
        my_error(ER_ERROR_DURING_ROLLBACK, MYF(0), err);
        error=1;
      }
      statistic_increment(thd->status_var.ha_rollback_count,&LOCK_status);
      *ht= 0;
    }
    trans->nht=0;
    trans->no_2pc=0;
    if (is_real_trans)
    {
      if (thd->transaction_rollback_request)
        thd->transaction.xid_state.rm_error= thd->net.last_errno;
      else
        thd->transaction.xid_state.xid.null();
    }
    if (all)
      thd->variables.tx_isolation=thd->session_tx_isolation;
  }
  /* Always cleanup. Even if there nht==0. There may be savepoints. */
  if (all)
    thd->transaction.cleanup();
#endif /* USING_TRANSACTIONS */
  if (all)
    thd->transaction_rollback_request= FALSE;

  /*
    If a non-transactional table was updated, warn; don't warn if this is a
    slave thread (because when a slave thread executes a ROLLBACK, it has
    been read from the binary log, so it's 100% sure and normal to produce
    error ER_WARNING_NOT_COMPLETE_ROLLBACK. If we sent the warning to the
    slave SQL thread, it would not stop the thread but just be printed in
    the error log; but we don't want users to wonder why they have this
    message in the error log, so we don't send it.
  */
  if (is_real_trans && thd->transaction.all.modified_non_trans_table &&
      !thd->slave_thread)
    push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
                 ER_WARNING_NOT_COMPLETE_ROLLBACK,
                 ER(ER_WARNING_NOT_COMPLETE_ROLLBACK));
  DBUG_RETURN(error);
}

/*
  This is used to commit or rollback a single statement depending on the value
  of error. Note that if the autocommit is on, then the following call inside
  InnoDB will commit or rollback the whole transaction (= the statement). The
  autocommit mechanism built into InnoDB is based on counting locks, but if
  the user has used LOCK TABLES then that mechanism does not know to do the
  commit.
*/

int ha_autocommit_or_rollback(THD *thd, int error)
{
  DBUG_ENTER("ha_autocommit_or_rollback");
#ifdef USING_TRANSACTIONS
  if (thd->transaction.stmt.nht)
  {
    if (!error)
    {
      if (ha_commit_stmt(thd))
	error=1;
    }
    else if (thd->transaction_rollback_request && !thd->in_sub_stmt)
      (void) ha_rollback(thd);
    else
      (void) ha_rollback_stmt(thd);

    thd->variables.tx_isolation=thd->session_tx_isolation;
  }
#endif
  DBUG_RETURN(error);
}


int ha_commit_or_rollback_by_xid(XID *xid, bool commit)
{
  handlerton **types;
  int res= 1;

  for (types= sys_table_types; *types; types++)
  {
    if ((*types)->state == SHOW_OPTION_YES && (*types)->recover)
    {
      if ((*(commit ? (*types)->commit_by_xid :
             (*types)->rollback_by_xid))(xid))
        res= 0;
    }
  }
  return res;
}


#ifndef DBUG_OFF
/* this does not need to be multi-byte safe or anything */
static char* xid_to_str(char *buf, XID *xid)
{
  int i;
  char *s=buf;
  *s++='\'';
  for (i=0; i < xid->gtrid_length+xid->bqual_length; i++)
  {
    uchar c=(uchar)xid->data[i];
    /* is_next_dig is set if next character is a number */
    bool is_next_dig= FALSE;
    if (i < XIDDATASIZE)
    {
      char ch= xid->data[i+1];
      is_next_dig= (ch >= '0' && ch <='9');
    }
    if (i == xid->gtrid_length)
    {
      *s++='\'';
      if (xid->bqual_length)
      {
        *s++='.';
        *s++='\'';
      }
    }
    if (c < 32 || c > 126)
    {
      *s++='\\';
      /*
        If next character is a number, write current character with
        3 octal numbers to ensure that the next number is not seen
        as part of the octal number
      */
      if (c > 077 || is_next_dig)
        *s++=_dig_vec_lower[c >> 6];
      if (c > 007 || is_next_dig)
        *s++=_dig_vec_lower[(c >> 3) & 7];
      *s++=_dig_vec_lower[c & 7];
    }
    else
    {
      if (c == '\'' || c == '\\')
        *s++='\\';
      *s++=c;
    }
  }
  *s++='\'';
  *s=0;
  return buf;
}
#endif

/*
  recover() step of xa

  NOTE
   there are three modes of operation:

   - automatic recover after a crash
     in this case commit_list != 0, tc_heuristic_recover==0
     all xids from commit_list are committed, others are rolled back

   - manual (heuristic) recover
     in this case commit_list==0, tc_heuristic_recover != 0
     DBA has explicitly specified that all prepared transactions should
     be committed (or rolled back).

   - no recovery (MySQL did not detect a crash)
     in this case commit_list==0, tc_heuristic_recover == 0
     there should be no prepared transactions in this case.
*/
int ha_recover(HASH *commit_list)
{
  int len, got, found_foreign_xids=0, found_my_xids=0;
  handlerton **types;
  XID *list=0;
  bool dry_run=(commit_list==0 && tc_heuristic_recover==0);
  DBUG_ENTER("ha_recover");

  /* commit_list and tc_heuristic_recover cannot be set both */
  DBUG_ASSERT(commit_list==0 || tc_heuristic_recover==0);
  /* if either is set, total_ha_2pc must be set too */
  DBUG_ASSERT(dry_run || total_ha_2pc>(ulong)opt_bin_log);

  if (total_ha_2pc <= (ulong)opt_bin_log)
    DBUG_RETURN(0);

  if (commit_list)
    sql_print_information("Starting crash recovery...");

#ifndef WILL_BE_DELETED_LATER
  /*
    for now, only InnoDB supports 2pc. It means we can always safely
    rollback all pending transactions, without risking inconsistent data
  */
  DBUG_ASSERT(total_ha_2pc == (ulong) opt_bin_log+1); // only InnoDB and binlog
  tc_heuristic_recover= TC_HEURISTIC_RECOVER_ROLLBACK; // forcing ROLLBACK
  dry_run=FALSE;
#endif

  for (len= MAX_XID_LIST_SIZE ; list==0 && len > MIN_XID_LIST_SIZE; len/=2)
  {
    list=(XID *)my_malloc(len*sizeof(XID), MYF(0));
  }
  if (!list)
  {
    sql_print_error(ER(ER_OUTOFMEMORY), len*sizeof(XID));
    DBUG_RETURN(1);
  }

  for (types= sys_table_types; *types; types++)
  {
    if ((*types)->state != SHOW_OPTION_YES || !(*types)->recover)
      continue;
    while ((got=(*(*types)->recover)(list, len)) > 0 )
    {
      sql_print_information("Found %d prepared transaction(s) in %s",
                            got, (*types)->name);
      for (int i=0; i < got; i ++)
      {
        my_xid x=list[i].get_my_xid();
        if (!x) // not "mine" - that is generated by external TM
        {
#ifndef DBUG_OFF
          char buf[XIDDATASIZE*4+6]; // see xid_to_str
          sql_print_information("ignore xid %s", xid_to_str(buf, list+i));
#endif
          xid_cache_insert(list+i, XA_PREPARED);
          found_foreign_xids++;
          continue;
        }
        if (dry_run)
        {
          found_my_xids++;
          continue;
        }
        // recovery mode
        if (commit_list ?
            hash_search(commit_list, (byte *)&x, sizeof(x)) != 0 :
            tc_heuristic_recover == TC_HEURISTIC_RECOVER_COMMIT)
        {
#ifndef DBUG_OFF
          char buf[XIDDATASIZE*4+6]; // see xid_to_str
          sql_print_information("commit xid %s", xid_to_str(buf, list+i));
#endif
          (*(*types)->commit_by_xid)(list+i);
        }
        else
        {
#ifndef DBUG_OFF
          char buf[XIDDATASIZE*4+6]; // see xid_to_str
          sql_print_information("rollback xid %s", xid_to_str(buf, list+i));
#endif
          (*(*types)->rollback_by_xid)(list+i);
        }
      }
      if (got < len)
        break;
    }
  }
  my_free((gptr)list, MYF(0));
  if (found_foreign_xids)
    sql_print_warning("Found %d prepared XA transactions", found_foreign_xids);
  if (dry_run && found_my_xids)
  {
    sql_print_error("Found %d prepared transactions! It means that mysqld was "
                    "not shut down properly last time and critical recovery "
                    "information (last binlog or %s file) was manually deleted "
                    "after a crash. You have to start mysqld with "
                    "--tc-heuristic-recover switch to commit or rollback "
                    "pending transactions.",
                    found_my_xids, opt_tc_log_file);
    DBUG_RETURN(1);
  }
  if (commit_list)
    sql_print_information("Crash recovery finished.");
  DBUG_RETURN(0);
}

/*
  return the list of XID's to a client, the same way SHOW commands do

  NOTE
    I didn't find in XA specs that an RM cannot return the same XID twice,
    so mysql_xa_recover does not filter XID's to ensure uniqueness.
    It can be easily fixed later, if necessary.
*/
bool mysql_xa_recover(THD *thd)
{
  List<Item> field_list;
  Protocol *protocol= thd->protocol;
  int i=0;
  XID_STATE *xs;
  DBUG_ENTER("mysql_xa_recover");

  field_list.push_back(new Item_int("formatID", 0, MY_INT32_NUM_DECIMAL_DIGITS));
  field_list.push_back(new Item_int("gtrid_length", 0, MY_INT32_NUM_DECIMAL_DIGITS));
  field_list.push_back(new Item_int("bqual_length", 0, MY_INT32_NUM_DECIMAL_DIGITS));
  field_list.push_back(new Item_empty_string("data",XIDDATASIZE));

  if (protocol->send_fields(&field_list,
                            Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF))
    DBUG_RETURN(1);

  pthread_mutex_lock(&LOCK_xid_cache);
  while ((xs= (XID_STATE*)hash_element(&xid_cache, i++)))
  {
    if (xs->xa_state==XA_PREPARED)
    {
      protocol->prepare_for_resend();
      protocol->store_longlong((longlong)xs->xid.formatID, FALSE);
      protocol->store_longlong((longlong)xs->xid.gtrid_length, FALSE);
      protocol->store_longlong((longlong)xs->xid.bqual_length, FALSE);
      protocol->store(xs->xid.data, xs->xid.gtrid_length+xs->xid.bqual_length,
                      &my_charset_bin);
      if (protocol->write())
      {
        pthread_mutex_unlock(&LOCK_xid_cache);
        DBUG_RETURN(1);
      }
    }
  }

  pthread_mutex_unlock(&LOCK_xid_cache);
  send_eof(thd);
  DBUG_RETURN(0);
}

/*
  This function should be called when MySQL sends rows of a SELECT result set
  or the EOF mark to the client. It releases a possible adaptive hash index
  S-latch held by thd in InnoDB and also releases a possible InnoDB query
  FIFO ticket to enter InnoDB. To save CPU time, InnoDB allows a thd to
  keep them over several calls of the InnoDB handler interface when a join
  is executed. But when we let the control to pass to the client they have
  to be released because if the application program uses mysql_use_result(),
  it may deadlock on the S-latch if the application on another connection
  performs another SQL query. In MySQL-4.1 this is even more important because
  there a connection can have several SELECT queries open at the same time.

  arguments:
  thd:           the thread handle of the current connection
  return value:  always 0
*/

int ha_release_temporary_latches(THD *thd)
{
#ifdef HAVE_INNOBASE_DB
  if (opt_innodb)
    innobase_release_temporary_latches(thd);
#endif
  return 0;
}


/*
  Export statistics for different engines. Currently we use it only for
  InnoDB.
*/

int ha_update_statistics()
{
#ifdef HAVE_INNOBASE_DB
  if (opt_innodb)
    innodb_export_status();
#endif
  return 0;
}

int ha_rollback_to_savepoint(THD *thd, SAVEPOINT *sv)
{
  int error=0;
  THD_TRANS *trans= (thd->in_sub_stmt ? &thd->transaction.stmt :
                                        &thd->transaction.all);
  handlerton **ht=trans->ht, **end_ht;
  DBUG_ENTER("ha_rollback_to_savepoint");

  trans->nht=sv->nht;
  trans->no_2pc=0;
  end_ht=ht+sv->nht;
  /*
    rolling back to savepoint in all storage engines that were part of the
    transaction when the savepoint was set
  */
  for (; ht < end_ht; ht++)
  {
    int err;
    DBUG_ASSERT((*ht)->savepoint_set != 0);
    if ((err= (*(*ht)->savepoint_rollback)(thd, (byte *)(sv+1)+(*ht)->savepoint_offset)))
    { // cannot happen
      my_error(ER_ERROR_DURING_ROLLBACK, MYF(0), err);
      error=1;
    }
    statistic_increment(thd->status_var.ha_savepoint_rollback_count,&LOCK_status);
    trans->no_2pc|=(*ht)->prepare == 0;
  }
  /*
    rolling back the transaction in all storage engines that were not part of
    the transaction when the savepoint was set
  */
  for (; *ht ; ht++)
  {
    int err;
    if ((err= (*(*ht)->rollback)(thd, !thd->in_sub_stmt)))
    { // cannot happen
      my_error(ER_ERROR_DURING_ROLLBACK, MYF(0), err);
      error=1;
    }
    statistic_increment(thd->status_var.ha_rollback_count,&LOCK_status);
    *ht=0; // keep it conveniently zero-filled
  }
  DBUG_RETURN(error);
}

/*
  note, that according to the sql standard (ISO/IEC 9075-2:2003)
  section "4.33.4 SQL-statements and transaction states",
  SAVEPOINT is *not* transaction-initiating SQL-statement
*/

int ha_savepoint(THD *thd, SAVEPOINT *sv)
{
  int error=0;
  THD_TRANS *trans= (thd->in_sub_stmt ? &thd->transaction.stmt :
                                        &thd->transaction.all);
  handlerton **ht=trans->ht;
  DBUG_ENTER("ha_savepoint");
#ifdef USING_TRANSACTIONS
  for (; *ht; ht++)
  {
    int err;
    if (! (*ht)->savepoint_set)
    {
      my_error(ER_CHECK_NOT_IMPLEMENTED, MYF(0), "SAVEPOINT");
      error=1;
      break;
    }
    if ((err= (*(*ht)->savepoint_set)(thd, (byte *)(sv+1)+(*ht)->savepoint_offset)))
    { // cannot happen
      my_error(ER_GET_ERRNO, MYF(0), err);
      error=1;
    }
    statistic_increment(thd->status_var.ha_savepoint_count,&LOCK_status);
  }
  sv->nht=trans->nht;
#endif /* USING_TRANSACTIONS */
  DBUG_RETURN(error);
}

int ha_release_savepoint(THD *thd, SAVEPOINT *sv)
{
  int error=0;
  THD_TRANS *trans= (thd->in_sub_stmt ? &thd->transaction.stmt :
                                        &thd->transaction.all);
  handlerton **ht=trans->ht, **end_ht;
  DBUG_ENTER("ha_release_savepoint");

  end_ht=ht+sv->nht;
  for (; ht < end_ht; ht++)
  {
    int err;
    if (!(*ht)->savepoint_release)
      continue;
    if ((err= (*(*ht)->savepoint_release)(thd, (byte *)(sv+1)+(*ht)->savepoint_offset)))
    { // cannot happen
      my_error(ER_GET_ERRNO, MYF(0), err);
      error=1;
    }
  }
  DBUG_RETURN(error);
}


int ha_start_consistent_snapshot(THD *thd)
{
#ifdef HAVE_INNOBASE_DB
  if ((have_innodb == SHOW_OPTION_YES) &&
      !innobase_start_trx_and_assign_read_view(thd))
    return 0;
#endif
  /*
    Same idea as when one wants to CREATE TABLE in one engine which does not
    exist:
  */
  push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN, ER_UNKNOWN_ERROR,
               "This MySQL server does not support any "
               "consistent-read capable storage engine");
  return 0;
}


bool ha_flush_logs()
{
  bool result=0;
#ifdef HAVE_BERKELEY_DB
  if ((have_berkeley_db == SHOW_OPTION_YES) &&
      berkeley_flush_logs())
    result=1;
#endif
#ifdef HAVE_INNOBASE_DB
  if ((have_innodb == SHOW_OPTION_YES) &&
      innobase_flush_logs())
    result=1;
#endif
  return result;
}

/*
  This should return ENOENT if the file doesn't exists.
  The .frm file will be deleted only if we return 0 or ENOENT
*/

int ha_delete_table(THD *thd, enum db_type table_type, const char *path,
                    const char *alias, bool generate_warning)
{
  handler *file;
  char tmp_path[FN_REFLEN];
  int error;
  TABLE dummy_table;
  TABLE_SHARE dummy_share;
  DBUG_ENTER("ha_delete_table");

  bzero((char*) &dummy_table, sizeof(dummy_table));
  bzero((char*) &dummy_share, sizeof(dummy_share));
  dummy_table.s= &dummy_share;

  /* DB_TYPE_UNKNOWN is used in ALTER TABLE when renaming only .frm files */
  if (table_type == DB_TYPE_UNKNOWN ||
      ! (file=get_new_handler(&dummy_table, thd->mem_root, table_type)))
    DBUG_RETURN(ENOENT);

  if (lower_case_table_names == 2 && !(file->table_flags() & HA_FILE_BASED))
  {
    /* Ensure that table handler get path in lower case */
    strmov(tmp_path, path);
    my_casedn_str(files_charset_info, tmp_path);
    path= tmp_path;
  }
  if ((error= file->delete_table(path)) && generate_warning)
  {
    /*
      Because file->print_error() use my_error() to generate the error message
      we must store the error state in thd, reset it and restore it to
      be able to get hold of the error message.
      (We should in the future either rewrite handler::print_error() or make
      a nice method of this.
    */
    bool query_error= thd->query_error;
    sp_rcontext *spcont= thd->spcont;
    SELECT_LEX *current_select= thd->lex->current_select;
    char buff[sizeof(thd->net.last_error)];
    char new_error[sizeof(thd->net.last_error)];
    int last_errno= thd->net.last_errno;

    strmake(buff, thd->net.last_error, sizeof(buff)-1);
    thd->query_error= 0;
    thd->spcont= NULL;
    thd->lex->current_select= 0;
    thd->net.last_error[0]= 0;

    /* Fill up strucutures that print_error may need */
    dummy_table.s->path= path;
    dummy_table.alias= alias;

    file->print_error(error, 0);
    strmake(new_error, thd->net.last_error, sizeof(buff)-1);

    /* restore thd */
    thd->query_error= query_error;
    thd->spcont= spcont;
    thd->lex->current_select= current_select;
    thd->net.last_errno= last_errno;
    strmake(thd->net.last_error, buff, sizeof(buff)-1);
    push_warning(thd, MYSQL_ERROR::WARN_LEVEL_ERROR, error, new_error);
  }
  delete file;
  DBUG_RETURN(error);
}

/****************************************************************************
** General handler functions
****************************************************************************/
handler *handler::clone(MEM_ROOT *mem_root)
{
  handler *new_handler= get_new_handler(table, mem_root, table->s->db_type);
  /*
    Allocate handler->ref here because otherwise ha_open will allocate it
    on this->table->mem_root and we will not be able to reclaim that memory 
    when the clone handler object is destroyed.
  */
  if (!(new_handler->ref= (byte*) alloc_root(mem_root, ALIGN_SIZE(ref_length)*2)))
    return NULL;
  if (new_handler && !new_handler->ha_open(table->s->path, table->db_stat,
                                           HA_OPEN_IGNORE_IF_LOCKED))
    return new_handler;
  return NULL;
}


	/* Open database-handler. Try O_RDONLY if can't open as O_RDWR */
	/* Don't wait for locks if not HA_OPEN_WAIT_IF_LOCKED is set */

int handler::ha_open(const char *name, int mode, int test_if_locked)
{
  int error;
  DBUG_ENTER("handler::ha_open");
  DBUG_PRINT("enter",("name: %s  db_type: %d  db_stat: %d  mode: %d  lock_test: %d",
                      name, table->s->db_type, table->db_stat, mode,
                      test_if_locked));

  if ((error=open(name,mode,test_if_locked)))
  {
    if ((error == EACCES || error == EROFS) && mode == O_RDWR &&
	(table->db_stat & HA_TRY_READ_ONLY))
    {
      table->db_stat|=HA_READ_ONLY;
      error=open(name,O_RDONLY,test_if_locked);
    }
  }
  if (error)
  {
    my_errno=error;			/* Safeguard */
    DBUG_PRINT("error",("error: %d  errno: %d",error,errno));
  }
  else
  {
    if (table->s->db_options_in_use & HA_OPTION_READ_ONLY_DATA)
      table->db_stat|=HA_READ_ONLY;
    (void) extra(HA_EXTRA_NO_READCHECK);	// Not needed in SQL

    DBUG_ASSERT(alloc_root_inited(&table->mem_root));
    /* ref is already allocated for us if we're called from handler::clone() */
    if (!ref && !(ref= (byte*) alloc_root(&table->mem_root, 
                                          ALIGN_SIZE(ref_length)*2)))
    {
      close();
      error=HA_ERR_OUT_OF_MEM;
    }
    else
      dupp_ref=ref+ALIGN_SIZE(ref_length);
  }
  DBUG_RETURN(error);
}

/*
  Read first row (only) from a table
  This is never called for InnoDB or BDB tables, as these table types
  has the HA_NOT_EXACT_COUNT set.
*/

int handler::read_first_row(byte * buf, uint primary_key)
{
  register int error;
  DBUG_ENTER("handler::read_first_row");

  statistic_increment(current_thd->status_var.ha_read_first_count,&LOCK_status);

  /*
    If there is very few deleted rows in the table, find the first row by
    scanning the table.
    TODO remove the test for HA_READ_ORDER
  */
  if (deleted < 10 || primary_key >= MAX_KEY ||
      !(index_flags(primary_key, 0, 0) & HA_READ_ORDER))
  {
    (void) ha_rnd_init(1);
    while ((error= rnd_next(buf)) == HA_ERR_RECORD_DELETED) ;
    (void) ha_rnd_end();
  }
  else
  {
    /* Find the first row through the primary key */
    (void) ha_index_init(primary_key);
    error=index_first(buf);
    (void) ha_index_end();
  }
  DBUG_RETURN(error);
}

/*
  Generate the next auto-increment number based on increment and offset

  In most cases increment= offset= 1, in which case we get:
  1,2,3,4,5,...
  If increment=10 and offset=5 and previous number is 1, we get:
  1,5,15,25,35,...
*/

inline ulonglong
next_insert_id(ulonglong nr,struct system_variables *variables)
{
  nr= (((nr+ variables->auto_increment_increment -
         variables->auto_increment_offset)) /
       (ulonglong) variables->auto_increment_increment);
  return (nr* (ulonglong) variables->auto_increment_increment +
          variables->auto_increment_offset);
}


void handler::adjust_next_insert_id_after_explicit_value(ulonglong nr)
{
  /*
    If we have set THD::next_insert_id previously and plan to insert an
    explicitely-specified value larger than this, we need to increase
    THD::next_insert_id to be greater than the explicit value.
  */
  THD *thd= table->in_use;
  if (thd->clear_next_insert_id && (nr >= thd->next_insert_id))
  {
    if (thd->variables.auto_increment_increment != 1)
      nr= next_insert_id(nr, &thd->variables);
    else
      nr++;
    thd->next_insert_id= nr;
    DBUG_PRINT("info",("next_insert_id: %lu", (ulong) nr));
  }
}


/*
  Computes the largest number X:
  - smaller than or equal to "nr"
  - of the form: auto_increment_offset + N * auto_increment_increment
  where N>=0.

  SYNOPSIS
    prev_insert_id
      nr            Number to "round down"
      variables     variables struct containing auto_increment_increment and
                    auto_increment_offset

  RETURN
    The number X if it exists, "nr" otherwise.
*/

inline ulonglong
prev_insert_id(ulonglong nr, struct system_variables *variables)
{
  if (unlikely(nr < variables->auto_increment_offset))
  {
    /*
      There's nothing good we can do here. That is a pathological case, where
      the offset is larger than the column's max possible value, i.e. not even
      the first sequence value may be inserted. User will receive warning.
    */
    DBUG_PRINT("info",("auto_increment: nr: %lu cannot honour "
                       "auto_increment_offset: %lu",
                       (ulong) nr, variables->auto_increment_offset));
    return nr;
  }
  if (variables->auto_increment_increment == 1)
    return nr; // optimization of the formula below
  nr= (((nr - variables->auto_increment_offset)) /
       (ulonglong) variables->auto_increment_increment);
  return (nr * (ulonglong) variables->auto_increment_increment +
          variables->auto_increment_offset);
}


/*
  Update the auto_increment field if necessary

  SYNOPSIS
     update_auto_increment()

  RETURN
    0	ok
    HA_ERR_AUTOINC_READ_FAILED
     	get_auto_increment() was called and returned ~(ulonglong) 0
    HA_ERR_AUTOINC_ERANGE
        storing value in field caused strict mode failure.


  IMPLEMENTATION

    Updates columns with type NEXT_NUMBER if:

  - If column value is set to NULL (in which case
    auto_increment_field_not_null is 0)
  - If column is set to 0 and (sql_mode & MODE_NO_AUTO_VALUE_ON_ZERO) is not
    set. In the future we will only set NEXT_NUMBER fields if one sets them
    to NULL (or they are not included in the insert list).


  There are two different cases when the above is true:

  - thd->next_insert_id == 0  (This is the normal case)
    In this case we set the set the column for the first row to the value
    next_insert_id(get_auto_increment(column))) which is normally
    max-used-column-value +1.

    We call get_auto_increment() only for the first row in a multi-row
    statement. For the following rows we generate new numbers based on the
    last used number.

  - thd->next_insert_id != 0.  This happens when we have read a statement
    from the binary log or when one has used SET LAST_INSERT_ID=#.

    In this case we will set the column to the value of next_insert_id.
    The next row will be given the id
    next_insert_id(next_insert_id)

    The idea is that generated auto_increment values are predictable and
    independent of the column values in the table.  This is needed to be
    able to replicate into a table that already has rows with a higher
    auto-increment value than the one that is inserted.

    After we have already generated an auto-increment number and the user
    inserts a column with a higher value than the last used one, we will
    start counting from the inserted value.

    thd->next_insert_id is cleared after it's been used for a statement.
*/

int handler::update_auto_increment()
{
  ulonglong nr;
  THD *thd= table->in_use;
  struct system_variables *variables= &thd->variables;
  bool external_auto_increment= 
       table->file->table_flags() & HA_EXTERNAL_AUTO_INCREMENT;
  DBUG_ENTER("handler::update_auto_increment");

  /*
    We must save the previous value to be able to restore it if the
    row was not inserted
  */
  thd->prev_insert_id= thd->next_insert_id;

  if ((nr= table->next_number_field->val_int()) != 0 ||
      (table->auto_increment_field_not_null &&
      thd->variables.sql_mode & MODE_NO_AUTO_VALUE_ON_ZERO))
  {
    /* Mark that we didn't generate a new value **/
    auto_increment_column_changed=0;
    adjust_next_insert_id_after_explicit_value(nr);
    DBUG_RETURN(0);
  }
  if (external_auto_increment || !(nr= thd->next_insert_id))
  {
    if ((nr= get_auto_increment()) == ~(ulonglong) 0)
      DBUG_RETURN(HA_ERR_AUTOINC_READ_FAILED);  // Mark failure

    if (!external_auto_increment && variables->auto_increment_increment != 1)
      nr= next_insert_id(nr-1, variables);
    /*
      Update next row based on the found value. This way we don't have to
      call the handler for every generated auto-increment value on a
      multi-row statement
    */
    thd->next_insert_id= nr;
  }

  DBUG_PRINT("info",("auto_increment: %lu", (ulong) nr));

  /* Mark that we should clear next_insert_id before next stmt */
  thd->clear_next_insert_id= 1;

  if (likely(!table->next_number_field->store((longlong) nr, TRUE)))
    thd->insert_id((ulonglong) nr);
  else
  if (thd->killed != THD::KILL_BAD_DATA) /* did we fail strict mode? */
  {
    /*
      overflow of the field; we'll use the max value, however we try to
      decrease it to honour auto_increment_* variables:
    */
    nr= prev_insert_id(table->next_number_field->val_int(), variables);
    thd->insert_id(nr);
    if (unlikely(table->next_number_field->store((longlong) nr, TRUE)))
      thd->insert_id(nr= table->next_number_field->val_int());
  }
  else
    DBUG_RETURN(HA_ERR_AUTOINC_ERANGE);

  /*
    We can't set next_insert_id if the auto-increment key is not the
    first key part, as there is no guarantee that the first parts will be in
    sequence
  */
  if (!table->s->next_number_key_offset)
  {
    /*
      Set next insert id to point to next auto-increment value to be able to
      handle multi-row statements
      This works even if auto_increment_increment > 1
    */
    thd->next_insert_id= next_insert_id(nr, variables);
  }
  else
    thd->next_insert_id= 0;

  /* Mark that we generated a new value */
  auto_increment_column_changed=1;
  DBUG_RETURN(0);
}

/*
  restore_auto_increment

  In case of error on write, we restore the last used next_insert_id value
  because the previous value was not used.
*/

void handler::restore_auto_increment()
{
  THD *thd= table->in_use;
  if (thd->next_insert_id)
  {
    thd->next_insert_id= thd->prev_insert_id;
    if (thd->next_insert_id == 0)
    {
      /* we didn't generate a value, engine will be called again */
      thd->clear_next_insert_id= 0;
    }
  }
}


ulonglong handler::get_auto_increment()
{
  ulonglong nr;
  int error;

  (void) extra(HA_EXTRA_KEYREAD);
  index_init(table->s->next_number_index);
  if (!table->s->next_number_key_offset)
  {						// Autoincrement at key-start
    error=index_last(table->record[1]);
  }
  else
  {
    byte key[MAX_KEY_LENGTH];
    key_copy(key, table->record[0],
             table->key_info + table->s->next_number_index,
             table->s->next_number_key_offset);
    error= index_read(table->record[1], key, table->s->next_number_key_offset,
                      HA_READ_PREFIX_LAST);
  }

  if (error)
    nr=1;
  else
    nr= ((ulonglong) table->next_number_field->
         val_int_offset(table->s->rec_buff_length)+1);
  index_end();
  (void) extra(HA_EXTRA_NO_KEYREAD);
  return nr;
}


/*
  Print error that we got from handler function

  NOTE
   In case of delete table it's only safe to use the following parts of
   the 'table' structure:
     table->s->path
     table->alias
*/

void handler::print_error(int error, myf errflag)
{
  DBUG_ENTER("handler::print_error");
  DBUG_PRINT("enter",("error: %d",error));

  int textno=ER_GET_ERRNO;
  switch (error) {
  case EACCES:
    textno=ER_OPEN_AS_READONLY;
    break;
  case EAGAIN:
    textno=ER_FILE_USED;
    break;
  case ENOENT:
    textno=ER_FILE_NOT_FOUND;
    break;
  case HA_ERR_KEY_NOT_FOUND:
  case HA_ERR_NO_ACTIVE_RECORD:
  case HA_ERR_END_OF_FILE:
    textno=ER_KEY_NOT_FOUND;
    break;
  case HA_ERR_WRONG_MRG_TABLE_DEF:
    textno=ER_WRONG_MRG_TABLE;
    break;
  case HA_ERR_FOUND_DUPP_KEY:
  {
    uint key_nr=get_dup_key(error);
    if ((int) key_nr >= 0)
    {
      /* Write the dupplicated key in the error message */
      char key[MAX_KEY_LENGTH];
      String str(key,sizeof(key),system_charset_info);

      if (key_nr == MAX_KEY)
      {
	/* Key is unknown */
	str.copy("", 0, system_charset_info);
	key_nr= (uint) -1;
      }
      else
      {
	key_unpack(&str,table,(uint) key_nr);
	uint max_length=MYSQL_ERRMSG_SIZE-(uint) strlen(ER(ER_DUP_ENTRY));
	if (str.length() >= max_length)
	{
	    str.length(max_length-4);
	    str.append(STRING_WITH_LEN("..."));
	}
      }
      my_error(ER_DUP_ENTRY, MYF(0), str.c_ptr(), key_nr+1);
      DBUG_VOID_RETURN;
    }
    textno=ER_DUP_KEY;
    break;
  }
  case HA_ERR_NULL_IN_SPATIAL:
    my_error(ER_CANT_CREATE_GEOMETRY_OBJECT, MYF(0));
    DBUG_VOID_RETURN;
  case HA_ERR_FOUND_DUPP_UNIQUE:
    textno=ER_DUP_UNIQUE;
    break;
  case HA_ERR_RECORD_CHANGED:
    textno=ER_CHECKREAD;
    break;
  case HA_ERR_CRASHED:
    textno=ER_NOT_KEYFILE;
    break;
  case HA_ERR_WRONG_IN_RECORD:
    textno= ER_CRASHED_ON_USAGE;
    break;
  case HA_ERR_CRASHED_ON_USAGE:
    textno=ER_CRASHED_ON_USAGE;
    break;
  case HA_ERR_NOT_A_TABLE:
    textno= error;
    break;
  case HA_ERR_CRASHED_ON_REPAIR:
    textno=ER_CRASHED_ON_REPAIR;
    break;
  case HA_ERR_OUT_OF_MEM:
    textno=ER_OUT_OF_RESOURCES;
    break;
  case HA_ERR_WRONG_COMMAND:
    textno=ER_ILLEGAL_HA;
    break;
  case HA_ERR_OLD_FILE:
    textno=ER_OLD_KEYFILE;
    break;
  case HA_ERR_UNSUPPORTED:
    textno=ER_UNSUPPORTED_EXTENSION;
    break;
  case HA_ERR_RECORD_FILE_FULL:
  case HA_ERR_INDEX_FILE_FULL:
    textno=ER_RECORD_FILE_FULL;
    break;
  case HA_ERR_LOCK_WAIT_TIMEOUT:
    textno=ER_LOCK_WAIT_TIMEOUT;
    break;
  case HA_ERR_LOCK_TABLE_FULL:
    textno=ER_LOCK_TABLE_FULL;
    break;
  case HA_ERR_LOCK_DEADLOCK:
    textno=ER_LOCK_DEADLOCK;
    break;
  case HA_ERR_READ_ONLY_TRANSACTION:
    textno=ER_READ_ONLY_TRANSACTION;
    break;
  case HA_ERR_CANNOT_ADD_FOREIGN:
    textno=ER_CANNOT_ADD_FOREIGN;
    break;
  case HA_ERR_ROW_IS_REFERENCED:
  {
    String str;
    get_error_message(error, &str);
    my_error(ER_ROW_IS_REFERENCED_2, MYF(0), str.c_ptr_safe());
    DBUG_VOID_RETURN;
  }
  case HA_ERR_NO_REFERENCED_ROW:
  {
    String str;
    get_error_message(error, &str);
    my_error(ER_NO_REFERENCED_ROW_2, MYF(0), str.c_ptr_safe());
    DBUG_VOID_RETURN;
  }
  case HA_ERR_TABLE_DEF_CHANGED:
    textno=ER_TABLE_DEF_CHANGED;
    break;
  case HA_ERR_NO_SUCH_TABLE:
  {
    /*
      We have to use path to find database name instead of using
      table->table_cache_key because if the table didn't exist, then
      table_cache_key was not set up
    */
    char *db;
    char buff[FN_REFLEN];
    uint length= dirname_part(buff,table->s->path);
    buff[length-1]=0;
    db=buff+dirname_length(buff);
    my_error(ER_NO_SUCH_TABLE, MYF(0), db, table->alias);
    break;
  }
  case HA_ERR_TABLE_NEEDS_UPGRADE:
    textno=ER_TABLE_NEEDS_UPGRADE;
    break;
  case HA_ERR_TABLE_READONLY:
    textno= ER_OPEN_AS_READONLY;
    break;
  case HA_ERR_AUTOINC_READ_FAILED:
    textno= ER_AUTOINC_READ_FAILED;
    break;
  case HA_ERR_AUTOINC_ERANGE:
    textno= ER_WARN_DATA_OUT_OF_RANGE;
    break;
  case HA_ERR_TOO_MANY_CONCURRENT_TRXS:
    textno= ER_TOO_MANY_CONCURRENT_TRXS;
    break;
  default:
    {
      /* The error was "unknown" to this function.
	 Ask handler if it has got a message for this error */
      bool temporary= FALSE;
      String str;
      temporary= get_error_message(error, &str);
      if (!str.is_empty())
      {
	const char* engine= table_type();
	if (temporary)
	  my_error(ER_GET_TEMPORARY_ERRMSG, MYF(0), error, str.ptr(), engine);
	else
	  my_error(ER_GET_ERRMSG, MYF(0), error, str.ptr(), engine);
      }
      else
	my_error(ER_GET_ERRNO,errflag,error);
      DBUG_VOID_RETURN;
    }
  }
  my_error(textno, errflag, table->alias, error);
  DBUG_VOID_RETURN;
}


/*
   Return an error message specific to this handler

   SYNOPSIS
   error        error code previously returned by handler
   buf          Pointer to String where to add error message

   Returns true if this is a temporary error
 */

bool handler::get_error_message(int error, String* buf)
{
  return FALSE;
}


/**
  Check for incompatible collation changes.
   
  @retval
    HA_ADMIN_NEEDS_UPGRADE   Table may have data requiring upgrade.
  @retval
    0                        No upgrade required.
*/

int handler::check_collation_compatibility()
{
  ulong mysql_version= table->s->mysql_version;

  if (mysql_version < 50048)
  {
    KEY *key= table->key_info;
    KEY *key_end= key + table->s->keys;
    for (; key < key_end; key++)
    {
      KEY_PART_INFO *key_part= key->key_part;
      KEY_PART_INFO *key_part_end= key_part + key->key_parts;
      for (; key_part < key_part_end; key_part++)
      {
        if (!key_part->fieldnr)
          continue;
        Field *field= table->field[key_part->fieldnr - 1];
        uint cs_number= field->charset()->number;
        if (mysql_version < 50048 &&
            (cs_number == 11 || /* ascii_general_ci - bug #29499, bug #27562 */
             cs_number == 41 || /* latin7_general_ci - bug #29461 */
             cs_number == 42 || /* latin7_general_cs - bug #29461 */
             cs_number == 20 || /* latin7_estonian_cs - bug #29461 */
             cs_number == 21 || /* latin2_hungarian_ci - bug #29461 */
             cs_number == 22 || /* koi8u_general_ci - bug #29461 */
             cs_number == 23 || /* cp1251_ukrainian_ci - bug #29461 */
             cs_number == 26))  /* cp1250_general_ci - bug #29461 */
          return HA_ADMIN_NEEDS_UPGRADE;
      }  
    }  
  }  
  return 0;
}


int handler::ha_check_for_upgrade(HA_CHECK_OPT *check_opt)
{
  int error;
  KEY *keyinfo, *keyend;
  KEY_PART_INFO *keypart, *keypartend;

  if (!table->s->mysql_version)
  {
    /* check for blob-in-key error */
    keyinfo= table->key_info;
    keyend= table->key_info + table->s->keys;
    for (; keyinfo < keyend; keyinfo++)
    {
      keypart= keyinfo->key_part;
      keypartend= keypart + keyinfo->key_parts;
      for (; keypart < keypartend; keypart++)
      {
        if (!keypart->fieldnr)
          continue;
        Field *field= table->field[keypart->fieldnr-1];
        if (field->type() == FIELD_TYPE_BLOB)
        {
          if (check_opt->sql_flags & TT_FOR_UPGRADE)
            check_opt->flags= T_MEDIUM;
          return HA_ADMIN_NEEDS_CHECK;
        }
      }
    }
  }
  if (table->s->frm_version != FRM_VER_TRUE_VARCHAR)
    return HA_ADMIN_NEEDS_ALTER;

  if ((error= check_collation_compatibility()))
      return error;

  return check_for_upgrade(check_opt);
}


int handler::check_old_types()
{
  Field** field;

  if (!table->s->mysql_version)
  {
    /* check for bad DECIMAL field */
    for (field= table->field; (*field); field++)
    {
      if ((*field)->type() == FIELD_TYPE_NEWDECIMAL)
      {
        return HA_ADMIN_NEEDS_ALTER;
      }
      if ((*field)->type() == MYSQL_TYPE_VAR_STRING)
      {
        return HA_ADMIN_NEEDS_ALTER;
      }
    }
  }
  return 0;
}


static bool update_frm_version(TABLE *table, bool needs_lock)
{
  char path[FN_REFLEN];
  File file;
  int result= 1;
  DBUG_ENTER("update_frm_version");

  /*
    No need to update frm version in case table was created or checked
    by server with the same version. This also ensures that we do not
    update frm version for temporary tables as this code doesn't support
    temporary tables.
  */
  if (table->s->mysql_version == MYSQL_VERSION_ID)
    DBUG_RETURN(0);

  strxnmov(path, sizeof(path)-1, mysql_data_home, "/", table->s->db, "/",
           table->s->table_name, reg_ext, NullS);
  if (!unpack_filename(path, path))
    DBUG_RETURN(1);

  if (needs_lock)
    pthread_mutex_lock(&LOCK_open);

  if ((file= my_open(path, O_RDWR|O_BINARY, MYF(MY_WME))) >= 0)
  {
    uchar version[4];
    char *key= table->s->table_cache_key;
    uint key_length= table->s->key_length;
    TABLE *entry;
    HASH_SEARCH_STATE state;

    int4store(version, MYSQL_VERSION_ID);

    if ((result= my_pwrite(file,(byte*) version,4,51L,MYF_RW)))
      goto err;

    for (entry=(TABLE*) hash_first(&open_cache,(byte*) key,key_length, &state);
         entry;
         entry= (TABLE*) hash_next(&open_cache,(byte*) key,key_length, &state))
      entry->s->mysql_version= MYSQL_VERSION_ID;
  }
err:
  if (file >= 0)
    VOID(my_close(file,MYF(MY_WME)));
  if (needs_lock)
    pthread_mutex_unlock(&LOCK_open);
  DBUG_RETURN(result);
}



/* Return key if error because of duplicated keys */

uint handler::get_dup_key(int error)
{
  DBUG_ENTER("handler::get_dup_key");
  table->file->errkey  = (uint) -1;
  if (error == HA_ERR_FOUND_DUPP_KEY || error == HA_ERR_FOUND_DUPP_UNIQUE ||
      error == HA_ERR_NULL_IN_SPATIAL)
    info(HA_STATUS_ERRKEY | HA_STATUS_NO_LOCK);
  DBUG_RETURN(table->file->errkey);
}


/*
  Delete all files with extension from bas_ext()

  SYNOPSIS
    delete_table()
    name		Base name of table

  NOTES
    We assume that the handler may return more extensions than
    was actually used for the file.

  RETURN
    0   If we successfully deleted at least one file from base_ext and
	didn't get any other errors than ENOENT
    #   Error
*/

int handler::delete_table(const char *name)
{
  int error= 0;
  int enoent_or_zero= ENOENT;                   // Error if no file was deleted
  char buff[FN_REFLEN];

  for (const char **ext=bas_ext(); *ext ; ext++)
  {
    fn_format(buff, name, "", *ext, 2 | 4);
    if (my_delete_with_symlink(buff, MYF(0)))
    {
      if ((error= my_errno) != ENOENT)
	break;
    }
    else
      enoent_or_zero= 0;                        // No error for ENOENT
    error= enoent_or_zero;
  }
  return error;
}


int handler::rename_table(const char * from, const char * to)
{
  int error= 0;
  for (const char **ext= bas_ext(); *ext ; ext++)
  {
    if (rename_file_ext(from, to, *ext))
    {
      if ((error=my_errno) != ENOENT)
	break;
      error= 0;
    }
  }
  return error;
}


/*
   Performs checks upon the table.

   SYNOPSIS
   check()
   thd                thread doing CHECK TABLE operation
   check_opt          options from the parser

   NOTES

   RETURN
   HA_ADMIN_OK                 Successful upgrade
   HA_ADMIN_NEEDS_UPGRADE      Table has structures requiring upgrade
   HA_ADMIN_NEEDS_ALTER        Table has structures requiring ALTER TABLE
   HA_ADMIN_NOT_IMPLEMENTED
*/

int handler::ha_check(THD *thd, HA_CHECK_OPT *check_opt)
{
  int error;

  if ((table->s->mysql_version >= MYSQL_VERSION_ID) &&
      (check_opt->sql_flags & TT_FOR_UPGRADE))
    return 0;

  if (table->s->mysql_version < MYSQL_VERSION_ID)
  {
    if ((error= check_old_types()))
      return error;
    error= ha_check_for_upgrade(check_opt);
    if (error && (error != HA_ADMIN_NEEDS_CHECK))
      return error;
    if (!error && (check_opt->sql_flags & TT_FOR_UPGRADE))
      return 0;
  }
  if ((error= check(thd, check_opt)))
    return error;
  return update_frm_version(table, 0);
}


int handler::ha_repair(THD* thd, HA_CHECK_OPT* check_opt)
{
  int result;
  if ((result= repair(thd, check_opt)))
    return result;
  return update_frm_version(table, 0);
}


/*
  Tell the storage engine that it is allowed to "disable transaction" in the
  handler. It is a hint that ACID is not required - it is used in NDB for
  ALTER TABLE, for example, when data are copied to temporary table.
  A storage engine may treat this hint any way it likes. NDB for example
  starts to commit every now and then automatically.
  This hint can be safely ignored.
*/

int ha_enable_transaction(THD *thd, bool on)
{
  int error=0;

  DBUG_ENTER("ha_enable_transaction");
  thd->transaction.on= on;
  if (on)
  {
    /*
      Now all storage engines should have transaction handling enabled.
      But some may have it enabled all the time - "disabling" transactions
      is an optimization hint that storage engine is free to ignore.
      So, let's commit an open transaction (if any) now.
    */
    if (!(error= ha_commit_stmt(thd)))
      error= end_trans(thd, COMMIT);
  }
  DBUG_RETURN(error);
}

int handler::index_next_same(byte *buf, const byte *key, uint keylen)
{
  int error;
  if (!(error=index_next(buf)))
  {
    if (key_cmp_if_same(table, key, active_index, keylen))
    {
      table->status=STATUS_NOT_FOUND;
      error=HA_ERR_END_OF_FILE;
    }
  }
  return error;
}


/****************************************************************************
** Some general functions that isn't in the handler class
****************************************************************************/

/*
  Initiates table-file and calls apropriate database-creator
  Returns 1 if something got wrong
*/

int ha_create_table(const char *name, HA_CREATE_INFO *create_info,
		    bool update_create_info)
{
  int error;
  TABLE table;
  char name_buff[FN_REFLEN];
  DBUG_ENTER("ha_create_table");

  if (openfrm(current_thd, name,"",0,(uint) READ_ALL, 0, &table))
    DBUG_RETURN(1);
  if (update_create_info)
  {
    update_create_info_from_table(create_info, &table);
  }
  if (lower_case_table_names == 2 &&
      !(table.file->table_flags() & HA_FILE_BASED))
  {
    /* Ensure that handler gets name in lower case */
    strmov(name_buff, name);
    my_casedn_str(files_charset_info, name_buff);
    name= name_buff;
  }

  error=table.file->create(name,&table,create_info);
  VOID(closefrm(&table));
  if (error)
    my_error(ER_CANT_CREATE_TABLE, MYF(ME_BELL+ME_WAITTANG), name,error);
  DBUG_RETURN(error != 0);
}

/*
  Try to discover table from engine and
  if found, write the frm file to disk.

  RETURN VALUES:
  -1 : Table did not exists
   0 : Table created ok
   > 0 : Error, table existed but could not be created

*/

int ha_create_table_from_engine(THD* thd,
				const char *db,
				const char *name)
{
  int error;
  const void *frmblob;
  uint frmlen;
  char path[FN_REFLEN];
  HA_CREATE_INFO create_info;
  TABLE table;
  DBUG_ENTER("ha_create_table_from_engine");
  DBUG_PRINT("enter", ("name '%s'.'%s'", db, name));

  bzero((char*) &create_info,sizeof(create_info));
  if ((error= ha_discover(thd, db, name, &frmblob, &frmlen)))
  {
    /* Table could not be discovered and thus not created */
    DBUG_RETURN(error);
  }

  /*
    Table exists in handler and could be discovered
    frmblob and frmlen are set, write the frm to disk
  */

  (void)strxnmov(path,FN_REFLEN,mysql_data_home,"/",db,"/",name,NullS);
  // Save the frm file
  error= writefrm(path, frmblob, frmlen);
  my_free((char*) frmblob, MYF(0));
  if (error)
    DBUG_RETURN(2);

  if (openfrm(thd, path,"",0,(uint) READ_ALL, 0, &table))
    DBUG_RETURN(3);

  update_create_info_from_table(&create_info, &table);
  create_info.table_options|= HA_OPTION_CREATE_FROM_ENGINE;

  if (lower_case_table_names == 2 &&
      !(table.file->table_flags() & HA_FILE_BASED))
  {
    /* Ensure that handler gets name in lower case */
    my_casedn_str(files_charset_info, path);
  }
  error=table.file->create(path,&table,&create_info);
  VOID(closefrm(&table));

  DBUG_RETURN(error != 0);
}

void st_ha_check_opt::init()
{
  flags= sql_flags= 0;
  sort_buffer_size = current_thd->variables.myisam_sort_buff_size;
}


/*****************************************************************************
  Key cache handling.

  This code is only relevant for ISAM/MyISAM tables

  key_cache->cache may be 0 only in the case where a key cache is not
  initialized or when we where not able to init the key cache in a previous
  call to ha_init_key_cache() (probably out of memory)
*****************************************************************************/

/* Init a key cache if it has not been initied before */


int ha_init_key_cache(const char *name, KEY_CACHE *key_cache)
{
  DBUG_ENTER("ha_init_key_cache");

  if (!key_cache->key_cache_inited)
  {
    pthread_mutex_lock(&LOCK_global_system_variables);
    ulong tmp_buff_size= (ulong) key_cache->param_buff_size;
    uint tmp_block_size= (uint) key_cache->param_block_size;
    uint division_limit= key_cache->param_division_limit;
    uint age_threshold=  key_cache->param_age_threshold;
    pthread_mutex_unlock(&LOCK_global_system_variables);
    DBUG_RETURN(!init_key_cache(key_cache,
				tmp_block_size,
				tmp_buff_size,
				division_limit, age_threshold));
  }
  DBUG_RETURN(0);
}


/* Resize key cache */

int ha_resize_key_cache(KEY_CACHE *key_cache)
{
  DBUG_ENTER("ha_resize_key_cache");

  if (key_cache->key_cache_inited)
  {
    pthread_mutex_lock(&LOCK_global_system_variables);
    long tmp_buff_size= (long) key_cache->param_buff_size;
    long tmp_block_size= (long) key_cache->param_block_size;
    uint division_limit= key_cache->param_division_limit;
    uint age_threshold=  key_cache->param_age_threshold;
    pthread_mutex_unlock(&LOCK_global_system_variables);
    DBUG_RETURN(!resize_key_cache(key_cache, tmp_block_size,
				  tmp_buff_size,
				  division_limit, age_threshold));
  }
  DBUG_RETURN(0);
}


/* Change parameters for key cache (like size) */

int ha_change_key_cache_param(KEY_CACHE *key_cache)
{
  if (key_cache->key_cache_inited)
  {
    pthread_mutex_lock(&LOCK_global_system_variables);
    uint division_limit= key_cache->param_division_limit;
    uint age_threshold=  key_cache->param_age_threshold;
    pthread_mutex_unlock(&LOCK_global_system_variables);
    change_key_cache_param(key_cache, division_limit, age_threshold);
  }
  return 0;
}

/* Free memory allocated by a key cache */

int ha_end_key_cache(KEY_CACHE *key_cache)
{
  end_key_cache(key_cache, 1);		// Can never fail
  return 0;
}

/* Move all tables from one key cache to another one */

int ha_change_key_cache(KEY_CACHE *old_key_cache,
			KEY_CACHE *new_key_cache)
{
  mi_change_key_cache(old_key_cache, new_key_cache);
  return 0;
}


/*
  Try to discover one table from handler(s)

  RETURN
   -1  : Table did not exists
    0  : OK. In this case *frmblob and *frmlen are set
    >0 : error.  frmblob and frmlen may not be set
*/

int ha_discover(THD *thd, const char *db, const char *name,
		const void **frmblob, uint *frmlen)
{
  int error= -1; // Table does not exist in any handler
  DBUG_ENTER("ha_discover");
  DBUG_PRINT("enter", ("db: %s, name: %s", db, name));
  if (is_prefix(name,tmp_file_prefix)) /* skip temporary tables */
    DBUG_RETURN(error);
#ifdef HAVE_NDBCLUSTER_DB
  if (have_ndbcluster == SHOW_OPTION_YES)
    error= ndbcluster_discover(thd, db, name, frmblob, frmlen);
#endif
  if (!error)
    statistic_increment(thd->status_var.ha_discover_count,&LOCK_status);
  DBUG_RETURN(error);
}


/*
  Call this function in order to give the handler the possiblity
  to ask engine if there are any new tables that should be written to disk
  or any dropped tables that need to be removed from disk
*/

int
ha_find_files(THD *thd,const char *db,const char *path,
	      const char *wild, bool dir, List<char> *files)
{
  int error= 0;
  DBUG_ENTER("ha_find_files");
  DBUG_PRINT("enter", ("db: %s, path: %s, wild: %s, dir: %d",
		       db, path, wild, dir));
#ifdef HAVE_NDBCLUSTER_DB
  if (have_ndbcluster == SHOW_OPTION_YES)
    error= ndbcluster_find_files(thd, db, path, wild, dir, files);
#endif
  DBUG_RETURN(error);
}


/*
  Ask handler if the table exists in engine

  RETURN
    HA_ERR_NO_SUCH_TABLE     Table does not exist
    HA_ERR_TABLE_EXIST       Table exists
    #                        Error code

 */
int ha_table_exists_in_engine(THD* thd, const char* db, const char* name)
{
  int error= HA_ERR_NO_SUCH_TABLE;
  DBUG_ENTER("ha_table_exists_in_engine");
  DBUG_PRINT("enter", ("db: %s, name: %s", db, name));
#ifdef HAVE_NDBCLUSTER_DB
  if (have_ndbcluster == SHOW_OPTION_YES)
    error= ndbcluster_table_exists_in_engine(thd, db, name);
#endif
  DBUG_PRINT("exit", ("error: %d", error));
  DBUG_RETURN(error);
}


/*
  Read the first row of a multi-range set.

  SYNOPSIS
    read_multi_range_first()
    found_range_p       Returns a pointer to the element in 'ranges' that
                        corresponds to the returned row.
    ranges              An array of KEY_MULTI_RANGE range descriptions.
    range_count         Number of ranges in 'ranges'.
    sorted		If result should be sorted per key.
    buffer              A HANDLER_BUFFER for internal handler usage.

  NOTES
    Record is read into table->record[0].
    *found_range_p returns a valid value only if read_multi_range_first()
    returns 0.
    Sorting is done within each range. If you want an overall sort, enter
    'ranges' with sorted ranges.

  RETURN
    0			OK, found a row
    HA_ERR_END_OF_FILE	No rows in range
    #			Error code
*/

int handler::read_multi_range_first(KEY_MULTI_RANGE **found_range_p,
                                    KEY_MULTI_RANGE *ranges, uint range_count,
                                    bool sorted, HANDLER_BUFFER *buffer)
{
  int result= HA_ERR_END_OF_FILE;
  DBUG_ENTER("handler::read_multi_range_first");
  multi_range_sorted= sorted;
  multi_range_buffer= buffer;

  for (multi_range_curr= ranges, multi_range_end= ranges + range_count;
       multi_range_curr < multi_range_end;
       multi_range_curr++)
  {
    result= read_range_first(multi_range_curr->start_key.length ?
                             &multi_range_curr->start_key : 0,
                             multi_range_curr->end_key.length ?
                             &multi_range_curr->end_key : 0,
                             test(multi_range_curr->range_flag & EQ_RANGE),
                             multi_range_sorted);
    if (result != HA_ERR_END_OF_FILE)
      break;
  }

  *found_range_p= multi_range_curr;
  DBUG_PRINT("exit",("result %d", result));
  DBUG_RETURN(result);
}


/*
  Read the next row of a multi-range set.

  SYNOPSIS
    read_multi_range_next()
    found_range_p       Returns a pointer to the element in 'ranges' that
                        corresponds to the returned row.

  NOTES
    Record is read into table->record[0].
    *found_range_p returns a valid value only if read_multi_range_next()
    returns 0.

  RETURN
    0			OK, found a row
    HA_ERR_END_OF_FILE	No (more) rows in range
    #			Error code
*/

int handler::read_multi_range_next(KEY_MULTI_RANGE **found_range_p)
{
  int result;
  DBUG_ENTER("handler::read_multi_range_next");

  /* We should not be called after the last call returned EOF. */
  DBUG_ASSERT(multi_range_curr < multi_range_end);

  do
  {
    /* Save a call if there can be only one row in range. */
    if (multi_range_curr->range_flag != (UNIQUE_RANGE | EQ_RANGE))
    {
      result= read_range_next();

      /* On success or non-EOF errors jump to the end. */
      if (result != HA_ERR_END_OF_FILE)
        break;
    }
    else
    {
      /*
        We need to set this for the last range only, but checking this
        condition is more expensive than just setting the result code.
      */
      result= HA_ERR_END_OF_FILE;
    }

    /* Try the next range(s) until one matches a record. */
    for (multi_range_curr++;
         multi_range_curr < multi_range_end;
         multi_range_curr++)
    {
      result= read_range_first(multi_range_curr->start_key.length ?
                               &multi_range_curr->start_key : 0,
                               multi_range_curr->end_key.length ?
                               &multi_range_curr->end_key : 0,
                               test(multi_range_curr->range_flag & EQ_RANGE),
                               multi_range_sorted);
      if (result != HA_ERR_END_OF_FILE)
        break;
    }
  }
  while ((result == HA_ERR_END_OF_FILE) &&
         (multi_range_curr < multi_range_end));

  *found_range_p= multi_range_curr;
  DBUG_PRINT("exit",("handler::read_multi_range_next: result %d", result));
  DBUG_RETURN(result);
}


/*
  Read first row between two ranges.
  Store ranges for future calls to read_range_next

  SYNOPSIS
    read_range_first()
    start_key		Start key. Is 0 if no min range
    end_key		End key.  Is 0 if no max range
    eq_range_arg	Set to 1 if start_key == end_key and the range endpoints
                        will not change during query execution.
    sorted		Set to 1 if result should be sorted per key

  NOTES
    Record is read into table->record[0]

  RETURN
    0			Found row
    HA_ERR_END_OF_FILE	No rows in range
    #			Error code
*/

int handler::read_range_first(const key_range *start_key,
			      const key_range *end_key,
			      bool eq_range_arg, bool sorted)
{
  int result;
  DBUG_ENTER("handler::read_range_first");

  eq_range= eq_range_arg;
  end_range= 0;
  if (end_key)
  {
    end_range= &save_end_range;
    save_end_range= *end_key;
    key_compare_result_on_equal= ((end_key->flag == HA_READ_BEFORE_KEY) ? 1 :
				  (end_key->flag == HA_READ_AFTER_KEY) ? -1 : 0);
  }
  range_key_part= table->key_info[active_index].key_part;

  if (!start_key)			// Read first record
    result= index_first(table->record[0]);
  else
    result= index_read(table->record[0],
		       start_key->key,
		       start_key->length,
		       start_key->flag);
  if (result)
    DBUG_RETURN((result == HA_ERR_KEY_NOT_FOUND)
		? HA_ERR_END_OF_FILE
		: result);

  DBUG_RETURN (compare_key(end_range) <= 0 ? 0 : HA_ERR_END_OF_FILE);
}


/*
  Read next row between two ranges.

  SYNOPSIS
    read_range_next()

  NOTES
    Record is read into table->record[0]

  RETURN
    0			Found row
    HA_ERR_END_OF_FILE	No rows in range
    #			Error code
*/

int handler::read_range_next()
{
  int result;
  DBUG_ENTER("handler::read_range_next");

  if (eq_range)
  {
    /* We trust that index_next_same always gives a row in range */
    DBUG_RETURN(index_next_same(table->record[0],
                                end_range->key,
                                end_range->length));
  }
  result= index_next(table->record[0]);
  if (result)
    DBUG_RETURN(result);
  DBUG_RETURN(compare_key(end_range) <= 0 ? 0 : HA_ERR_END_OF_FILE);
}


/*
  Compare if found key (in row) is over max-value

  SYNOPSIS
    compare_key
    range		range to compare to row. May be 0 for no range

  NOTES
    See key.cc::key_cmp() for details

  RETURN
    The return value is SIGN(key_in_row - range_key):

    0			Key is equal to range or 'range' == 0 (no range)
   -1			Key is less than range
    1			Key is larger than range
*/

int handler::compare_key(key_range *range)
{
  int cmp;
  if (!range)
    return 0;					// No max range
  cmp= key_cmp(range_key_part, range->key, range->length);
  if (!cmp)
    cmp= key_compare_result_on_equal;
  return cmp;
}

int handler::index_read_idx(byte * buf, uint index, const byte * key,
			     uint key_len, enum ha_rkey_function find_flag)
{
  int error= ha_index_init(index);
  if (!error)
    error= index_read(buf, key, key_len, find_flag);
  if (!error)
    error= ha_index_end();
  return error;
}


/*
  Returns a list of all known extensions.

  SYNOPSIS
    ha_known_exts()

  NOTES
    No mutexes, worst case race is a minor surplus memory allocation
    We have to recreate the extension map if mysqld is restarted (for example
    within libmysqld)

  RETURN VALUE
    pointer		pointer to TYPELIB structure
*/

TYPELIB *ha_known_exts(void)
{
  MEM_ROOT *mem_root= current_thd->mem_root;
  if (!known_extensions.type_names || mysys_usage_id != known_extensions_id)
  {
    handlerton **types;
    List<char> found_exts;
    List_iterator_fast<char> it(found_exts);
    const char **ext, *old_ext;

    known_extensions_id= mysys_usage_id;
    found_exts.push_back((char*) triggers_file_ext);
    found_exts.push_back((char*) trigname_file_ext);
    for (types= sys_table_types; *types; types++)
    {
      if ((*types)->state == SHOW_OPTION_YES)
      {
	handler *file= get_new_handler(0, mem_root,
                                       (enum db_type) (*types)->db_type);
	for (ext= file->bas_ext(); *ext; ext++)
	{
	  while ((old_ext= it++))
          {
	    if (!strcmp(old_ext, *ext))
	      break;
          }
	  if (!old_ext)
	    found_exts.push_back((char *) *ext);

	  it.rewind();
	}
	delete file;
      }
    }
    ext= (const char **) my_once_alloc(sizeof(char *)*
                                       (found_exts.elements+1),
                                       MYF(MY_WME | MY_FAE));

    DBUG_ASSERT(ext != 0);
    known_extensions.count= found_exts.elements;
    known_extensions.type_names= ext;

    while ((old_ext= it++))
      *ext++= old_ext;
    *ext= 0;
  }
  return &known_extensions;
}