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/* 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 "myisamdef.h"
static ha_rows _mi_record_pos(MI_INFO *info,const byte *key,uint key_len,
enum ha_rkey_function search_flag);
static double _mi_search_pos(MI_INFO *info,MI_KEYDEF *keyinfo,uchar *key,
uint key_len,uint nextflag,my_off_t pos);
static uint _mi_keynr(MI_INFO *info,MI_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 HA_POS_ERROR on error */
ha_rows mi_records_in_range(MI_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)
{
ha_rows start_pos,end_pos;
DBUG_ENTER("mi_records_in_range");
if ((inx = _mi_check_index(info,inx)) < 0)
DBUG_RETURN(HA_POS_ERROR);
if (fast_mi_readinfo(info))
DBUG_RETURN(HA_POS_ERROR);
info->update&= (HA_STATE_CHANGED+HA_STATE_ROW_CHANGED);
if (info->s->concurrent_insert)
rw_rdlock(&info->s->key_root_lock[inx]);
start_pos= (start_key ?
_mi_record_pos(info,start_key,start_key_len,start_search_flag) :
(ha_rows) 0);
end_pos= (end_key ?
_mi_record_pos(info,end_key,end_key_len,end_search_flag) :
info->state->records+ (ha_rows) 1);
if (info->s->concurrent_insert)
rw_unlock(&info->s->key_root_lock[inx]);
fast_mi_writeinfo(info);
if (start_pos == HA_POS_ERROR || end_pos == HA_POS_ERROR)
DBUG_RETURN(HA_POS_ERROR);
DBUG_PRINT("info",("records: %ld",(ulong) (end_pos-start_pos)));
DBUG_RETURN(end_pos < start_pos ? (ha_rows) 0 :
(end_pos == start_pos ? (ha_rows) 1 : end_pos-start_pos));
}
/* Find relative position (in records) for key in index-tree */
static ha_rows _mi_record_pos(MI_INFO *info, const byte *key, uint key_len,
enum ha_rkey_function search_flag)
{
uint inx=(uint) info->lastinx, nextflag;
MI_KEYDEF *keyinfo=info->s->keyinfo+inx;
uchar *key_buff;
double pos;
DBUG_ENTER("_mi_record_pos");
DBUG_PRINT("enter",("search_flag: %d",search_flag));
if (key_len == 0)
key_len=USE_WHOLE_KEY;
key_buff=info->lastkey+info->s->base.max_key_length;
key_len=_mi_pack_key(info,inx,key_buff,(uchar*) key,key_len);
DBUG_EXECUTE("key",_mi_print_key(DBUG_FILE,keyinfo->seg,
(uchar*) key_buff,key_len););
nextflag=myisam_read_vec[search_flag];
if (!(nextflag & (SEARCH_FIND | SEARCH_NO_FIND | SEARCH_LAST)))
key_len=USE_WHOLE_KEY;
pos=_mi_search_pos(info,keyinfo,key_buff,key_len,
nextflag | SEARCH_SAVE_BUFF,
info->s->state.key_root[inx]);
if (pos >= 0.0)
{
DBUG_PRINT("exit",("pos: %ld",(ulong) (pos*info->state->records)));
DBUG_RETURN((ulong) (pos*info->state->records+0.5));
}
DBUG_RETURN(HA_POS_ERROR);
}
/* This is a modified version of _mi_search */
/* Returns offset for key in indextable (decimal 0.0 <= x <= 1.0) */
static double _mi_search_pos(register MI_INFO *info,
register MI_KEYDEF *keyinfo,
uchar *key, uint key_len, uint nextflag,
register my_off_t pos)
{
int flag;
uint nod_flag,keynr,max_keynr;
my_bool after_key;
uchar *keypos,*buff;
double offset;
DBUG_ENTER("_mi_search_pos");
if (pos == HA_OFFSET_ERROR)
DBUG_RETURN(0.5);
if (!(buff=_mi_fetch_keypage(info,keyinfo,pos,info->buff,1)))
goto err;
flag=(*keyinfo->bin_search)(info,keyinfo,buff,key,key_len,nextflag,
&keypos,info->lastkey, &after_key);
nod_flag=mi_test_if_nod(buff);
keynr=_mi_keynr(info,keyinfo,buff,keypos,&max_keynr);
if (flag)
{
if (flag == MI_FOUND_WRONG_KEY)
DBUG_RETURN(-1); /* error */
/*
** Didn't found match. keypos points at next (bigger) key
* Try to find a smaller, better matching key.
** Matches keynr + [0-1]
*/
if (flag > 0 && ! nod_flag)
offset= 1.0;
else if ((offset=_mi_search_pos(info,keyinfo,key,key_len,nextflag,
_mi_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) && nod_flag &&
((keyinfo->flag & (HA_NOSAME | HA_NULL_PART)) != HA_NOSAME ||
key_len != USE_WHOLE_KEY))
{
/*
** There may be identical keys in the tree. Try to match on of those.
** Matches keynr + [0-1]
*/
if ((offset=_mi_search_pos(info,keyinfo,key,key_len,SEARCH_FIND,
_mi_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 _mi_keynr(MI_INFO *info, register MI_KEYDEF *keyinfo, uchar *page, uchar *keypos, uint *ret_max_key)
{
uint nod_flag,keynr,max_key;
uchar t_buff[MI_MAX_KEY_BUFF],*end;
end= page+mi_getint(page);
nod_flag=mi_test_if_nod(page);
page+=2+nod_flag;
if (!(keyinfo->flag & (HA_VAR_LENGTH_KEY| HA_BINARY_PACK_KEY)))
{
*ret_max_key= (uint) (end-page)/(keyinfo->keylength+nod_flag);
return (uint) (keypos-page)/(keyinfo->keylength+nod_flag);
}
max_key=keynr=0;
t_buff[0]=0; /* Safety */
while (page < end)
{
if (!(*keyinfo->get_key)(keyinfo,nod_flag,&page,t_buff))
return 0; /* Error */
max_key++;
if (page == keypos)
keynr=max_key;
}
*ret_max_key=max_key;
return(keynr);
}
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