mirror of
https://github.com/MariaDB/server.git
synced 2025-01-18 13:02:28 +01:00
d0c6eb885d
For "count(*) while index_column = value" an index read is done. It consists of an index scan and retrieval of each key. For efficiency reasons the index scan stores the key in the special buffer 'lastkey2' once only. At the first iteration it notes this fact with the flag HA_STATE_RNEXT_SAME in 'info->update'. For efficiency reasons, the key retrieval for blobs does not allocate a new buffer, but uses 'lastkey2'... Now I clear the HA_STATE_RNEXT_SAME flag whenever the buffer has been polluted. In this case, the index scan copies the key value again (and sets the flag again).
105 lines
3.2 KiB
C
105 lines
3.2 KiB
C
/* 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 */
|
|
|
|
#include "myisamdef.h"
|
|
#include "rt_index.h"
|
|
|
|
/*
|
|
Read next row with the same key as previous read, but abort if
|
|
the key changes.
|
|
One may have done a write, update or delete of the previous row.
|
|
NOTE! Even if one changes the previous row, the next read is done
|
|
based on the position of the last used key!
|
|
*/
|
|
|
|
int mi_rnext_same(MI_INFO *info, byte *buf)
|
|
{
|
|
int error;
|
|
uint inx,not_used[2];
|
|
MI_KEYDEF *keyinfo;
|
|
DBUG_ENTER("mi_rnext_same");
|
|
|
|
if ((int) (inx=info->lastinx) < 0 || info->lastpos == HA_OFFSET_ERROR)
|
|
DBUG_RETURN(my_errno=HA_ERR_WRONG_INDEX);
|
|
keyinfo=info->s->keyinfo+inx;
|
|
if (fast_mi_readinfo(info))
|
|
DBUG_RETURN(my_errno);
|
|
|
|
if (info->s->concurrent_insert)
|
|
rw_rdlock(&info->s->key_root_lock[inx]);
|
|
|
|
switch (keyinfo->key_alg)
|
|
{
|
|
#ifdef HAVE_RTREE_KEYS
|
|
case HA_KEY_ALG_RTREE:
|
|
if ((error=rtree_find_next(info,inx,
|
|
myisam_read_vec[info->last_key_func])))
|
|
{
|
|
error=1;
|
|
my_errno=HA_ERR_END_OF_FILE;
|
|
info->lastpos= HA_OFFSET_ERROR;
|
|
break;
|
|
}
|
|
break;
|
|
#endif
|
|
case HA_KEY_ALG_BTREE:
|
|
default:
|
|
if (!(info->update & HA_STATE_RNEXT_SAME))
|
|
{
|
|
/* First rnext_same; Store old key */
|
|
memcpy(info->lastkey2,info->lastkey,info->last_rkey_length);
|
|
}
|
|
for (;;)
|
|
{
|
|
if ((error=_mi_search_next(info,keyinfo,info->lastkey,
|
|
info->lastkey_length,SEARCH_BIGGER,
|
|
info->s->state.key_root[inx])))
|
|
break;
|
|
if (ha_key_cmp(keyinfo->seg, info->lastkey, info->lastkey2,
|
|
info->last_rkey_length, SEARCH_FIND, not_used))
|
|
{
|
|
error=1;
|
|
my_errno=HA_ERR_END_OF_FILE;
|
|
info->lastpos= HA_OFFSET_ERROR;
|
|
break;
|
|
}
|
|
/* Skip rows that are inserted by other threads since we got a lock */
|
|
if (info->lastpos < info->state->data_file_length)
|
|
break;
|
|
}
|
|
}
|
|
if (info->s->concurrent_insert)
|
|
rw_unlock(&info->s->key_root_lock[inx]);
|
|
/* Don't clear if database-changed */
|
|
info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED);
|
|
info->update|= HA_STATE_NEXT_FOUND | HA_STATE_RNEXT_SAME;
|
|
|
|
if (error)
|
|
{
|
|
if (my_errno == HA_ERR_KEY_NOT_FOUND)
|
|
my_errno=HA_ERR_END_OF_FILE;
|
|
}
|
|
else if (!buf)
|
|
{
|
|
DBUG_RETURN(info->lastpos==HA_OFFSET_ERROR ? my_errno : 0);
|
|
}
|
|
else if (!(*info->read_record)(info,info->lastpos,buf))
|
|
{
|
|
info->update|= HA_STATE_AKTIV; /* Record is read */
|
|
DBUG_RETURN(0);
|
|
}
|
|
DBUG_RETURN(my_errno);
|
|
} /* mi_rnext_same */
|