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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 */
/* Functions to check if a row is unique */
#include "myisamdef.h"
#include <m_ctype.h>
my_bool mi_check_unique(MI_INFO *info, MI_UNIQUEDEF *def, byte *record,
ha_checksum unique_hash, my_off_t disk_pos)
{
my_off_t lastpos=info->lastpos;
MI_KEYDEF *key= &info->s->keyinfo[def->key];
uchar *key_buff=info->lastkey2;
DBUG_ENTER("mi_check_unique");
mi_unique_store(record+key->seg->start, unique_hash);
_mi_make_key(info,def->key,key_buff,record,0);
if (_mi_search(info,info->s->keyinfo+def->key,key_buff,MI_UNIQUE_HASH_LENGTH,
SEARCH_FIND,info->s->state.key_root[def->key]))
{
info->page_changed=1; /* Can't optimize read next */
info->lastpos= lastpos;
DBUG_RETURN(0); /* No matching rows */
}
for (;;)
{
if (info->lastpos != disk_pos &&
!(*info->s->compare_unique)(info,def,record,info->lastpos))
{
my_errno=HA_ERR_FOUND_DUPP_UNIQUE;
info->errkey= (int) def->key;
info->dupp_key_pos= info->lastpos;
info->page_changed=1; /* Can't optimize read next */
info->lastpos=lastpos;
DBUG_PRINT("info",("Found duplicate"));
DBUG_RETURN(1); /* Found identical */
}
if (_mi_search_next(info,info->s->keyinfo+def->key, info->lastkey,
MI_UNIQUE_HASH_LENGTH, SEARCH_BIGGER,
info->s->state.key_root[def->key]) ||
bcmp(info->lastkey, key_buff, MI_UNIQUE_HASH_LENGTH))
{
info->page_changed=1; /* Can't optimize read next */
info->lastpos=lastpos;
DBUG_RETURN(0); /* end of tree */
}
}
}
/* Calculate a hash for a row */
ha_checksum mi_unique_hash(MI_UNIQUEDEF *def, const byte *record)
{
const byte *pos, *end;
ha_checksum crc=0;
MI_KEYSEG *keyseg;
for (keyseg=def->seg ; keyseg < def->end ; keyseg++)
{
enum ha_base_keytype type=(enum ha_base_keytype) keyseg->type;
uint length=keyseg->length;
if (keyseg->null_bit)
{
if (record[keyseg->null_pos] & keyseg->null_bit)
{
/*
Change crc in a way different from an empty string or 0.
(This is an optimisation; The code will work even if this isn't
done)
*/
crc=((crc << 8) + 511+
(crc >> (8*sizeof(ha_checksum)-8)));
continue;
}
}
pos= record+keyseg->start;
if (keyseg->flag & HA_VAR_LENGTH)
{
uint tmp_length=uint2korr(pos);
pos+=2; /* Skip VARCHAR length */
set_if_smaller(length,tmp_length);
}
else if (keyseg->flag & HA_BLOB_PART)
{
uint tmp_length=_mi_calc_blob_length(keyseg->bit_start,pos);
memcpy_fixed((byte*) &pos,pos+keyseg->bit_start,sizeof(char*));
if (!length || length > tmp_length)
length=tmp_length; /* The whole blob */
}
end= pos+length;
if (type == HA_KEYTYPE_TEXT || type == HA_KEYTYPE_VARTEXT)
{
uchar *sort_order=keyseg->charset->sort_order;
while (pos != end)
crc=((crc << 8) +
(((uchar) sort_order[*(uchar*) pos++]))) +
(crc >> (8*sizeof(ha_checksum)-8));
}
else
while (pos != end)
crc=((crc << 8) +
(((uchar) *(uchar*) pos++))) +
(crc >> (8*sizeof(ha_checksum)-8));
}
return crc;
}
/*
Returns 0 if both rows have equal unique value
*/
int mi_unique_comp(MI_UNIQUEDEF *def, const byte *a, const byte *b,
my_bool null_are_equal)
{
const byte *pos_a, *pos_b, *end;
MI_KEYSEG *keyseg;
for (keyseg=def->seg ; keyseg < def->end ; keyseg++)
{
enum ha_base_keytype type=(enum ha_base_keytype) keyseg->type;
uint length=keyseg->length;
/* If part is NULL it's regarded as different */
if (keyseg->null_bit)
{
uint tmp;
if ((tmp=(a[keyseg->null_pos] & keyseg->null_bit)) !=
(uint) (b[keyseg->null_pos] & keyseg->null_bit))
return 1;
if (tmp)
{
if (!null_are_equal)
return 1;
continue;
}
}
pos_a= a+keyseg->start;
pos_b= b+keyseg->start;
if (keyseg->flag & HA_VAR_LENGTH)
{
uint tmp_length=uint2korr(pos_a);
if (tmp_length != uint2korr(pos_b))
return 1;
pos_a+=2; /* Skip VARCHAR length */
pos_b+=2;
set_if_smaller(length,tmp_length);
}
else if (keyseg->flag & HA_BLOB_PART)
{
/* Only compare 'length' characters if length<> 0 */
uint a_length= _mi_calc_blob_length(keyseg->bit_start,pos_a);
uint b_length= _mi_calc_blob_length(keyseg->bit_start,pos_b);
/* Check that a and b are of equal length */
if (length && a_length > length)
a_length=length;
if (!length || length > b_length)
length=b_length;
if (length != a_length)
return 1;
/* Both strings are at least 'length' long */
memcpy_fixed((byte*) &pos_a,pos_a+keyseg->bit_start,sizeof(char*));
memcpy_fixed((byte*) &pos_b,pos_b+keyseg->bit_start,sizeof(char*));
}
if (type == HA_KEYTYPE_TEXT || type == HA_KEYTYPE_VARTEXT)
{
if (_mi_compare_text(keyseg->charset, (uchar *)pos_a, length,
(uchar *)pos_b, length, 0))
return 1;
}
else
{
end= pos_a+length;
while (pos_a != end)
if (*pos_a++ != *pos_b++)
return 1;
}
}
return 0;
}
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