mirror of
https://github.com/MariaDB/server.git
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203 lines
6.4 KiB
C
203 lines
6.4 KiB
C
/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult 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; either version 2 of the License, or
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(at your option) any later version.
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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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/*
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Gives a approximated number of how many records there is between two keys.
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Used when optimizing querries.
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*/
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#include "myisamdef.h"
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static ha_rows _mi_record_pos(MI_INFO *info,const byte *key,uint key_len,
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enum ha_rkey_function search_flag);
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static double _mi_search_pos(MI_INFO *info,MI_KEYDEF *keyinfo,uchar *key,
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uint key_len,uint nextflag,my_off_t pos);
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static uint _mi_keynr(MI_INFO *info,MI_KEYDEF *keyinfo,uchar *page,
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uchar *keypos,uint *ret_max_key);
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/* If start_key = 0 assume read from start */
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/* If end_key = 0 assume read to end */
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/* Returns HA_POS_ERROR on error */
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ha_rows mi_records_in_range(MI_INFO *info, int inx, const byte *start_key,
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uint start_key_len,
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enum ha_rkey_function start_search_flag,
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const byte *end_key, uint end_key_len,
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enum ha_rkey_function end_search_flag)
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{
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ha_rows start_pos,end_pos;
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DBUG_ENTER("mi_records_in_range");
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if ((inx = _mi_check_index(info,inx)) < 0)
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DBUG_RETURN(HA_POS_ERROR);
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if (fast_mi_readinfo(info))
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DBUG_RETURN(HA_POS_ERROR);
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info->update&= (HA_STATE_CHANGED+HA_STATE_ROW_CHANGED);
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if (info->s->concurrent_insert)
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rw_rdlock(&info->s->key_root_lock[inx]);
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start_pos= (start_key ?
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_mi_record_pos(info,start_key,start_key_len,start_search_flag) :
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(ha_rows) 0);
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end_pos= (end_key ?
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_mi_record_pos(info,end_key,end_key_len,end_search_flag) :
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info->state->records+ (ha_rows) 1);
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if (info->s->concurrent_insert)
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rw_unlock(&info->s->key_root_lock[inx]);
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fast_mi_writeinfo(info);
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if (start_pos == HA_POS_ERROR || end_pos == HA_POS_ERROR)
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DBUG_RETURN(HA_POS_ERROR);
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DBUG_PRINT("info",("records: %ld",(ulong) (end_pos-start_pos)));
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DBUG_RETURN(end_pos < start_pos ? (ha_rows) 0 :
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(end_pos == start_pos ? (ha_rows) 1 : end_pos-start_pos));
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}
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/* Find relative position (in records) for key in index-tree */
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static ha_rows _mi_record_pos(MI_INFO *info, const byte *key, uint key_len,
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enum ha_rkey_function search_flag)
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{
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uint inx=(uint) info->lastinx, nextflag;
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MI_KEYDEF *keyinfo=info->s->keyinfo+inx;
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uchar *key_buff;
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double pos;
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DBUG_ENTER("_mi_record_pos");
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DBUG_PRINT("enter",("search_flag: %d",search_flag));
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if (key_len == 0)
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key_len=USE_WHOLE_KEY;
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key_buff=info->lastkey+info->s->base.max_key_length;
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key_len=_mi_pack_key(info,inx,key_buff,(uchar*) key,key_len);
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DBUG_EXECUTE("key",_mi_print_key(DBUG_FILE,keyinfo->seg,
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(uchar*) key_buff,key_len););
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nextflag=myisam_read_vec[search_flag];
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if (!(nextflag & (SEARCH_FIND | SEARCH_NO_FIND | SEARCH_LAST)))
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key_len=USE_WHOLE_KEY;
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pos=_mi_search_pos(info,keyinfo,key_buff,key_len,
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nextflag | SEARCH_SAVE_BUFF,
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info->s->state.key_root[inx]);
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if (pos >= 0.0)
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{
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DBUG_PRINT("exit",("pos: %ld",(ulong) (pos*info->state->records)));
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DBUG_RETURN((ulong) (pos*info->state->records+0.5));
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}
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DBUG_RETURN(HA_POS_ERROR);
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}
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/* This is a modified version of _mi_search */
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/* Returns offset for key in indextable (decimal 0.0 <= x <= 1.0) */
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static double _mi_search_pos(register MI_INFO *info,
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register MI_KEYDEF *keyinfo,
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uchar *key, uint key_len, uint nextflag,
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register my_off_t pos)
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{
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int flag;
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uint nod_flag,keynr,max_keynr;
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my_bool after_key;
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uchar *keypos,*buff;
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double offset;
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DBUG_ENTER("_mi_search_pos");
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if (pos == HA_OFFSET_ERROR)
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DBUG_RETURN(0.5);
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if (!(buff=_mi_fetch_keypage(info,keyinfo,pos,info->buff,1)))
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goto err;
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flag=(*keyinfo->bin_search)(info,keyinfo,buff,key,key_len,nextflag,
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&keypos,info->lastkey, &after_key);
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nod_flag=mi_test_if_nod(buff);
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keynr=_mi_keynr(info,keyinfo,buff,keypos,&max_keynr);
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if (flag)
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{
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if (flag == MI_FOUND_WRONG_KEY)
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DBUG_RETURN(-1); /* error */
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/*
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** Didn't found match. keypos points at next (bigger) key
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* Try to find a smaller, better matching key.
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** Matches keynr + [0-1]
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*/
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if (flag > 0 && ! nod_flag)
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offset= 1.0;
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else if ((offset=_mi_search_pos(info,keyinfo,key,key_len,nextflag,
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_mi_kpos(nod_flag,keypos))) < 0)
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DBUG_RETURN(offset);
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}
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else
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{
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/*
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** Found match. Keypos points at the start of the found key
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** Matches keynr+1
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*/
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offset=1.0; /* Matches keynr+1 */
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if ((nextflag & SEARCH_FIND) && nod_flag &&
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((keyinfo->flag & (HA_NOSAME | HA_NULL_PART)) != HA_NOSAME ||
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key_len != USE_WHOLE_KEY))
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{
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/*
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** There may be identical keys in the tree. Try to match on of those.
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** Matches keynr + [0-1]
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*/
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if ((offset=_mi_search_pos(info,keyinfo,key,key_len,SEARCH_FIND,
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_mi_kpos(nod_flag,keypos))) < 0)
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DBUG_RETURN(offset); /* Read error */
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}
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}
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DBUG_PRINT("info",("keynr: %d offset: %g max_keynr: %d nod: %d flag: %d",
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keynr,offset,max_keynr,nod_flag,flag));
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DBUG_RETURN((keynr+offset)/(max_keynr+1));
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err:
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DBUG_PRINT("exit",("Error: %d",my_errno));
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DBUG_RETURN (-1.0);
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}
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/* Get keynummer of current key and max number of keys in nod */
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static uint _mi_keynr(MI_INFO *info, register MI_KEYDEF *keyinfo, uchar *page, uchar *keypos, uint *ret_max_key)
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{
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uint nod_flag,keynr,max_key;
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uchar t_buff[MI_MAX_KEY_BUFF],*end;
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end= page+mi_getint(page);
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nod_flag=mi_test_if_nod(page);
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page+=2+nod_flag;
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if (!(keyinfo->flag & (HA_VAR_LENGTH_KEY| HA_BINARY_PACK_KEY)))
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{
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*ret_max_key= (uint) (end-page)/(keyinfo->keylength+nod_flag);
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return (uint) (keypos-page)/(keyinfo->keylength+nod_flag);
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}
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max_key=keynr=0;
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t_buff[0]=0; /* Safety */
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while (page < end)
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{
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if (!(*keyinfo->get_key)(keyinfo,nod_flag,&page,t_buff))
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return 0; /* Error */
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max_key++;
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if (page == keypos)
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keynr=max_key;
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}
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*ret_max_key=max_key;
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return(keynr);
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}
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