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MDEV-27529 Wrong result upon query using index_merge with DESC key (#2)

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ROR-index_merge relies on Rowid-ordered-retrieval property: a ROR scan,
e.g. a scan on equality range

  tbl.key=const

should return rows ordered by their Rowid. Also, handler->cmp_ref() should
compare rowids according to the Rowid ordering.

When the table's primary key uses DESC keyparts, ROR scans return rows
according to the PK's ordering.

But ha_innobase::cmp_ref() compared rowids as if PK used ASC keyparts.
This caused wrong query results with index_merge.

Fixed this by making ha_innobase::cmp_ref() compare according to the PK
defintion, including keypart's DESC property.
This commit is contained in:
Sergei Petrunia
2022-01-19 10:05:50 +03:00
committed by Sergei Golubchik
parent 62760af4df
commit fca37e49bb
3 changed files with 53 additions and 2 deletions
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25
mysql-test/main/desc_index_range.result
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@@ -186,6 +186,29 @@ CREATE OR REPLACE TABLE t1 (pk INT, a INT, b int, KEY(a), PRIMARY KEY(pk DESC))
INSERT INTO t1 VALUES (1,4,5),(2,9,6),(3,NULL,7),(4,NULL,8);
SELECT * FROM t1 WHERE pk > 10 OR a > 0;
pk a b
1 4 5
2 9 6
1 4 5
DROP TABLE t1;
#
# MDEV-27529: Wrong result upon query using index_merge with DESC key (#2)
#
create table t1 (
pk int,
a int,
b int,
primary key(pk desc),
key(a),
key(b)
) engine=innodb;
insert into t1 values (0, 111111, 255);
insert into t1 select seq+50000, NULL, seq+1000 from seq_1_to_260;
insert into t1 values (10000, NULL, 255);
insert into t1 select seq+20000, seq+20000, seq+20000 from seq_1_to_1500;
# Must use ROR-intersect:
explain select * from t1 where b = 255 AND a IS NULL;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge a,b b,a 5,5 NULL 1 Using intersect(b,a); Using where; Using index
select * from t1 where b = 255 AND a IS NULL;
pk a b
10000 NULL 255
drop table t1;