range.c
上传用户:romrleung
上传日期:2022-05-23
资源大小:18897k
文件大小:6k
- /* 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 */
- /*
- Gives a approximated number of how many records there is between two keys.
- Used when optimizing querries.
- */
- #include "isamdef.h"
- static ulong _nisam_record_pos(N_INFO *info,const byte *key,uint key_len,
- enum ha_rkey_function search_flag);
- static double _nisam_search_pos(N_INFO *info,N_KEYDEF *keyinfo,uchar *key,
- uint key_len,uint nextflag,ulong pos);
- static uint _nisam_keynr(N_INFO *info,N_KEYDEF *keyinfo,uchar *page,
- uchar *keypos,uint *ret_max_key);
- /* If start_key = 0 assume read from start */
- /* If end_key = 0 assume read to end */
- /* Returns NI_POS_ERROR on error */
- ulong nisam_records_in_range(N_INFO *info, int inx, const byte *start_key,
- uint start_key_len,
- enum ha_rkey_function start_search_flag,
- const byte *end_key, uint end_key_len,
- enum ha_rkey_function end_search_flag)
- {
- ulong start_pos,end_pos;
- DBUG_ENTER("nisam_records_in_range");
- if ((inx = _nisam_check_index(info,inx)) < 0)
- DBUG_RETURN(NI_POS_ERROR);
- #ifndef NO_LOCKING
- if (_nisam_readinfo(info,F_RDLCK,1))
- DBUG_RETURN(NI_POS_ERROR);
- #endif
- info->update&= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED);
- start_pos= (start_key ?
- _nisam_record_pos(info,start_key,start_key_len,start_search_flag) :
- 0L);
- end_pos= (end_key ?
- _nisam_record_pos(info,end_key,end_key_len,end_search_flag) :
- info->s->state.records+1L);
- VOID(_nisam_writeinfo(info,0));
- if (start_pos == NI_POS_ERROR || end_pos == NI_POS_ERROR)
- DBUG_RETURN(NI_POS_ERROR);
- DBUG_PRINT("info",("records: %ld",end_pos-start_pos));
- DBUG_RETURN(end_pos < start_pos ? 0L :
- (end_pos == start_pos ? 1L : end_pos-start_pos));
- }
- /* Find relative position (in records) for key in index-tree */
- static ulong _nisam_record_pos(N_INFO *info, const byte *key, uint key_len,
- enum ha_rkey_function search_flag)
- {
- uint inx=(uint) info->lastinx;
- N_KEYDEF *keyinfo=info->s->keyinfo+inx;
- uchar *key_buff;
- double pos;
- DBUG_ENTER("_nisam_record_pos");
- DBUG_PRINT("enter",("search_flag: %d",search_flag));
- if (key_len >= (keyinfo->base.keylength-info->s->rec_reflength)
- && !(keyinfo->base.flag & HA_SPACE_PACK_USED))
- key_len=USE_HOLE_KEY;
- key_buff=info->lastkey+info->s->base.max_key_length;
- key_len=_nisam_pack_key(info,inx,key_buff,(uchar*) key,key_len);
- DBUG_EXECUTE("key",_nisam_print_key(DBUG_FILE,keyinfo->seg,
- (uchar*) key_buff););
- pos=_nisam_search_pos(info,keyinfo,key_buff,key_len,
- nisam_read_vec[search_flag] | SEARCH_SAVE_BUFF,
- info->s->state.key_root[inx]);
- if (pos >= 0.0)
- {
- DBUG_PRINT("exit",("pos: %ld",(ulong) (pos*info->s->state.records)));
- DBUG_RETURN((ulong) (pos*info->s->state.records+0.5));
- }
- DBUG_RETURN(NI_POS_ERROR);
- }
- /* This is a modified version of _nisam_search */
- /* Returns offset for key in indextable (decimal 0.0 <= x <= 1.0) */
- static double _nisam_search_pos(register N_INFO *info, register N_KEYDEF *keyinfo,
- uchar *key, uint key_len, uint nextflag,
- register ulong pos)
- {
- int flag;
- uint nod_flag,keynr,max_keynr;
- uchar *keypos,*buff;
- double offset;
- DBUG_ENTER("_nisam_search_pos");
- if (pos == NI_POS_ERROR)
- DBUG_RETURN(0.5);
- if (!(buff=_nisam_fetch_keypage(info,keyinfo,pos,info->buff,1)))
- goto err;
- flag=(*keyinfo->bin_search)(info,keyinfo,buff,key,key_len,nextflag,
- &keypos,info->lastkey);
- nod_flag=test_if_nod(buff);
- keynr=_nisam_keynr(info,keyinfo,buff,keypos,&max_keynr);
- if (flag)
- {
- /*
- ** Didn't found match. keypos points at next (bigger) key
- * Try to find a smaller, better matching key.
- ** Matches keynr + [0-1]
- */
- if ((offset=_nisam_search_pos(info,keyinfo,key,key_len,nextflag,
- _nisam_kpos(nod_flag,keypos))) < 0)
- DBUG_RETURN(offset);
- }
- else
- {
- /*
- ** Found match. Keypos points at the start of the found key
- ** Matches keynr+1
- */
- offset=1.0; /* Matches keynr+1 */
- if (nextflag & SEARCH_FIND && (!(keyinfo->base.flag & HA_NOSAME)
- || key_len) && nod_flag)
- {
- /*
- ** There may be identical keys in the tree. Try to match on of those.
- ** Matches keynr + [0-1]
- */
- if ((offset=_nisam_search_pos(info,keyinfo,key,key_len,SEARCH_FIND,
- _nisam_kpos(nod_flag,keypos))) < 0)
- DBUG_RETURN(offset); /* Read error */
- }
- }
- DBUG_PRINT("info",("keynr: %d offset: %g max_keynr: %d nod: %d flag: %d",
- keynr,offset,max_keynr,nod_flag,flag));
- DBUG_RETURN((keynr+offset)/(max_keynr+1));
- err:
- DBUG_PRINT("exit",("Error: %d",my_errno));
- DBUG_RETURN (-1.0);
- }
- /* Get keynummer of current key and max number of keys in nod */
- static uint _nisam_keynr(N_INFO *info, register N_KEYDEF *keyinfo, uchar *page, uchar *keypos, uint *ret_max_key)
- {
- uint nod_flag,keynr,max_key;
- uchar t_buff[N_MAX_KEY_BUFF],*end;
- end= page+getint(page);
- nod_flag=test_if_nod(page);
- page+=2+nod_flag;
- if (!(keyinfo->base.flag &
- (HA_PACK_KEY | HA_SPACE_PACK | HA_SPACE_PACK_USED)))
- {
- *ret_max_key= (uint) (end-page)/(keyinfo->base.keylength+nod_flag);
- return (uint) (keypos-page)/(keyinfo->base.keylength+nod_flag);
- }
- max_key=keynr=0;
- while (page < end)
- {
- t_buff[0]=0; /* Don't move packed key */
- VOID((*keyinfo->get_key)(keyinfo,nod_flag,&page,t_buff));
- max_key++;
- if (page == keypos)
- keynr=max_key;
- }
- *ret_max_key=max_key;
- return(keynr);
- }