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MDEV-19705: Assertion `tmp >= 0' failed in best_access_path

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The reason for hitting the assert is that rec_per_key estimates have some garbage value.
So the solution to fix this would be for long unique keys to use use rec_per_key for only 1 keypart,
that means rec_per_key[0] would have the estimate.
This commit is contained in:
Varun Gupta 2019-08-26 20:59:51 +05:30
parent 6afe013cde
commit 77e44282ff
3 changed files with 32 additions and 1 deletions
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15
mysql-test/main/long_unique.result
View File

@ -1462,4 +1462,19 @@ t1 CREATE TABLE `t1` (
KEY `pk` (`pk`,`a`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1
drop table t1;
#
# MDEV-19705: Assertion `tmp >= 0' failed in best_access_path
#
CREATE TABLE t1 (d varchar(10)) ENGINE=MyISAM;
INSERT INTO t1 VALUES ('a'),('q');
CREATE TABLE t2 (f varchar(10), a2 datetime, b int, a1 varchar(1024), pk int NOT NULL, PRIMARY KEY (pk), UNIQUE KEY (f,a1,a2), KEY f2 (f(4),a2)) ENGINE=MyISAM;
INSERT INTO t2 VALUES ('aaa','1985-09-06',-163,'s',1),('bbb','1995-01-05',3,'pucaz',2),('ccc','0000-00-00',NULL,'help',3),('ddd',NULL,618,'v',4),('eee','1995-12-20',410,'m',5),('ffq','1976-06-12 20:02:56',NULL,'POKNC',6),('dddd','0000-00-00',-328,'hgsu',7);
explain
SELECT t2.b FROM t1 JOIN t2 ON t1.d = t2.f WHERE t2.pk >= 20;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 range PRIMARY,f,f2 PRIMARY 4 NULL 1 Using index condition
1 SIMPLE t1 ALL NULL NULL NULL NULL 2 Using where; Using join buffer (flat, BNL join)
SELECT t2.b FROM t1 JOIN t2 ON t1.d = t2.f WHERE t2.pk >= 20;
b
drop table t1,t2;
set @@GLOBAL.max_allowed_packet= @allowed_packet;

14
mysql-test/main/long_unique.test
View File

@ -542,4 +542,18 @@ alter table t1 modify a varchar(1000);
show create table t1;
drop table t1;
--echo #
--echo # MDEV-19705: Assertion `tmp >= 0' failed in best_access_path
--echo #
CREATE TABLE t1 (d varchar(10)) ENGINE=MyISAM;
INSERT INTO t1 VALUES ('a'),('q');
CREATE TABLE t2 (f varchar(10), a2 datetime, b int, a1 varchar(1024), pk int NOT NULL, PRIMARY KEY (pk), UNIQUE KEY (f,a1,a2), KEY f2 (f(4),a2)) ENGINE=MyISAM;
INSERT INTO t2 VALUES ('aaa','1985-09-06',-163,'s',1),('bbb','1995-01-05',3,'pucaz',2),('ccc','0000-00-00',NULL,'help',3),('ddd',NULL,618,'v',4),('eee','1995-12-20',410,'m',5),('ffq','1976-06-12 20:02:56',NULL,'POKNC',6),('dddd','0000-00-00',-328,'hgsu',7);
explain
SELECT t2.b FROM t1 JOIN t2 ON t1.d = t2.f WHERE t2.pk >= 20;
SELECT t2.b FROM t1 JOIN t2 ON t1.d = t2.f WHERE t2.pk >= 20;
drop table t1,t2;
set @@GLOBAL.max_allowed_packet= @allowed_packet;

4
sql/table.cc
View File

@ -800,7 +800,8 @@ static bool create_key_infos(const uchar *strpos, const uchar *frm_image_end,
{
if (strpos + (new_frm_ver >= 1 ? 9 : 7) >= frm_image_end)
return 1;
*rec_per_key++=0;
if (!(keyinfo->algorithm == HA_KEY_ALG_LONG_HASH))
*rec_per_key++=0;
key_part->fieldnr= (uint16) (uint2korr(strpos) & FIELD_NR_MASK);
key_part->offset= (uint) uint2korr(strpos+2)-1;
key_part->key_type= (uint) uint2korr(strpos+5);
@ -828,6 +829,7 @@ static bool create_key_infos(const uchar *strpos, const uchar *frm_image_end,
{
keyinfo->key_length= HA_HASH_KEY_LENGTH_WITHOUT_NULL;
key_part++; // reserved for the hash value
*rec_per_key++=0;
}
/*