mi_preload.c
上传用户:romrleung
上传日期:2022-05-23
资源大小:18897k
文件大小:3k
- /* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult 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; 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
- /*
- Preload indexes into key cache
- */
- #include "myisamdef.h"
- /*
- Preload pages of the index file for a table into the key cache
- SYNOPSIS
- mi_preload()
- info open table
- map map of indexes to preload into key cache
- ignore_leaves only non-leaves pages are to be preloaded
- RETURN VALUE
- 0 if a success. error code - otherwise.
- NOTES.
- At present pages for all indexes are preloaded.
- In future only pages for indexes specified in the key_map parameter
- of the table will be preloaded.
- */
- int mi_preload(MI_INFO *info, ulonglong key_map, my_bool ignore_leaves)
- {
- uint i;
- ulong length, block_length= 0;
- uchar *buff= NULL;
- MYISAM_SHARE* share= info->s;
- uint keys= share->state.header.keys;
- MI_KEYDEF *keyinfo= share->keyinfo;
- my_off_t key_file_length= share->state.state.key_file_length;
- my_off_t pos= share->base.keystart;
- DBUG_ENTER("mi_preload");
- if (!keys || !key_map || key_file_length == pos)
- DBUG_RETURN(0);
- block_length= keyinfo[0].block_length;
- /* Check whether all indexes use the same block size */
- for (i= 1 ; i < keys ; i++)
- {
- if (keyinfo[i].block_length != block_length)
- DBUG_RETURN(my_errno= HA_ERR_NON_UNIQUE_BLOCK_SIZE);
- }
- length= info->preload_buff_size/block_length * block_length;
- set_if_bigger(length, block_length);
- if (!(buff= (uchar *) my_malloc(length, MYF(MY_WME))))
- DBUG_RETURN(my_errno= HA_ERR_OUT_OF_MEM);
- if (flush_key_blocks(share->key_cache,share->kfile, FLUSH_RELEASE))
- goto err;
- do
- {
- /* Read the next block of index file into the preload buffer */
- if ((my_off_t) length > (key_file_length-pos))
- length= (ulong) (key_file_length-pos);
- if (my_pread(share->kfile, (byte*) buff, length, pos, MYF(MY_FAE|MY_FNABP)))
- goto err;
- if (ignore_leaves)
- {
- uchar *end= buff+length;
- do
- {
- if (mi_test_if_nod(buff))
- {
- if (key_cache_insert(share->key_cache,
- share->kfile, pos, DFLT_INIT_HITS,
- (byte*) buff, block_length))
- goto err;
- }
- pos+= block_length;
- }
- while ((buff+= block_length) != end);
- buff= end-length;
- }
- else
- {
- if (key_cache_insert(share->key_cache,
- share->kfile, pos, DFLT_INIT_HITS,
- (byte*) buff, length))
- goto err;
- pos+= length;
- }
- }
- while (pos != key_file_length);
- my_free((char*) buff, MYF(0));
- DBUG_RETURN(0);
- err:
- my_free((char*) buff, MYF(MY_ALLOW_ZERO_PTR));
- DBUG_RETURN(my_errno= errno);
- }