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96e092dc73
WL#2474 "Multi Range Read: Change the default MRR implementation to implement new MRR interface"
WL#2475 "Batched range read functions for MyISAM/InnoDb"
"Index condition pushdown for MyISAM/InnoDB"
Igor's fix from sp1r-igor@olga.mysql.com-20080330055902-07614:
There could be observed the following problems:
1. EXPLAIN did not mention pushdown conditions from on expressions in the
'extra' column. As a result if a query had no where conditions pushed
down to a table, but had on conditions pushed to this table the 'extra'
column in the EXPLAIN for the table missed 'using where'.
2. Conditions for ref access were not eliminated from on expressions
though such conditions were eliminated from the where condition.
101 lines
3.2 KiB
C
101 lines
3.2 KiB
C
/* Copyright (C) 2000-2001, 2004 MySQL AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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#include "myisamdef.h"
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/*
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Read previous row with the same key as previous read
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One may have done a write, update or delete of the previous row.
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NOTE! Even if one changes the previous row, the next read is done
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based on the position of the last used key!
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*/
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int mi_rprev(MI_INFO *info, uchar *buf, int inx)
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{
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int error,changed;
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register uint flag;
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MYISAM_SHARE *share=info->s;
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DBUG_ENTER("mi_rprev");
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if ((inx = _mi_check_index(info,inx)) < 0)
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DBUG_RETURN(my_errno);
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flag=SEARCH_SMALLER; /* Read previous */
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if (info->lastpos == HA_OFFSET_ERROR && info->update & HA_STATE_NEXT_FOUND)
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flag=0; /* Read last */
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if (fast_mi_readinfo(info))
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DBUG_RETURN(my_errno);
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changed=_mi_test_if_changed(info);
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if (share->concurrent_insert)
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rw_rdlock(&share->key_root_lock[inx]);
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if (!flag)
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error=_mi_search_last(info, share->keyinfo+inx,
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share->state.key_root[inx]);
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else if (!changed)
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error=_mi_search_next(info,share->keyinfo+inx,info->lastkey,
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info->lastkey_length,flag,
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share->state.key_root[inx]);
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else
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error=_mi_search(info,share->keyinfo+inx,info->lastkey,
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USE_WHOLE_KEY, flag, share->state.key_root[inx]);
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if (!error)
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{
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int res= 0;
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while ((share->concurrent_insert &&
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info->lastpos >= info->state->data_file_length) ||
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(info->index_cond_func &&
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!(res= mi_check_index_cond(info, inx, buf))))
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{
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/*
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Skip rows that are either inserted by other threads since
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we got a lock or do not match pushed index conditions
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*/
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if ((error=_mi_search_next(info,share->keyinfo+inx,info->lastkey,
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info->lastkey_length,
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SEARCH_SMALLER,
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share->state.key_root[inx])))
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break;
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}
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if (!error && res == 2)
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{
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if (share->concurrent_insert)
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rw_unlock(&share->key_root_lock[inx]);
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info->lastpos= HA_OFFSET_ERROR;
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DBUG_RETURN(my_errno= HA_ERR_END_OF_FILE);
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}
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}
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if (share->concurrent_insert)
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rw_unlock(&share->key_root_lock[inx]);
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info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED);
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info->update|= HA_STATE_PREV_FOUND;
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if (error)
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{
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if (my_errno == HA_ERR_KEY_NOT_FOUND)
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my_errno=HA_ERR_END_OF_FILE;
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}
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else if (!buf)
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{
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DBUG_RETURN(info->lastpos==HA_OFFSET_ERROR ? my_errno : 0);
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}
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else if (!(*info->read_record)(info,info->lastpos,buf))
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{
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info->update|= HA_STATE_AKTIV; /* Record is read */
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DBUG_RETURN(0);
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}
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DBUG_RETURN(my_errno);
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} /* mi_rprev */
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