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MDEV-30333 Wrong result with not_null_range_scan and LEFT JOIN with empty table

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There was a bug in JOIN::make_notnull_conds_for_range_scans() when
clearing TABLE->tmp_set, which was used to mark fields that could not be
null.

This function was only used if 'not_null_range_scan=on' is set.

The effect was that tmp_set contained a 'random value' and this caused
the optimizer to think that some fields could not be null.
FLUSH TABLES clears tmp_set and because of this things worked temporarily.

Fixed by clearing tmp_set properly.
This commit is contained in:
Monty 2023-02-15 13:56:33 +02:00
parent 690fcfbd29
commit 192427e37d
3 changed files with 95 additions and 5 deletions

58
mysql-test/main/empty_table.result
View file

@ -16,3 +16,61 @@ ERROR 42S02: Table 'test.t2' doesn't exist
show status like "Empty_queries";
Variable_name Value
Empty_queries 2
# End of 4.1 tests
#
# MDEV-30333 Wrong result with not_null_range_scan and LEFT JOIN with empty table
#
set @save_optimizer_switch=@@optimizer_switch;
CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
INSERT INTO t1 (b) VALUES (1),(2);
CREATE TABLE t2 (c INT) ENGINE=MyISAM;
SET optimizer_switch= 'not_null_range_scan=off';
explain extended SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t2 system NULL NULL NULL NULL 0 0.00 Const row not found
1 SIMPLE t1 ALL NULL NULL NULL NULL 2 100.00 Using where; Using filesort
Warnings:
Note 1003 select `test`.`t1`.`b` AS `b` from `test`.`t1` where `test`.`t1`.`a` is null order by `test`.`t1`.`b`
SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
b
1
2
SET optimizer_switch = 'not_null_range_scan=on';
explain extended SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t2 system NULL NULL NULL NULL 0 0.00 Const row not found
1 SIMPLE t1 ALL NULL NULL NULL NULL 2 100.00 Using where; Using filesort
Warnings:
Note 1003 select `test`.`t1`.`b` AS `b` from `test`.`t1` where `test`.`t1`.`a` is null order by `test`.`t1`.`b`
SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
b
1
2
flush tables;
SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
b
1
2
drop table t1,t2;
# Second test in MDEV-30333
CREATE TABLE t1 (a int, b varchar(10)) ENGINE=MyISAM;
INSERT INTO t1 VALUES (69,'foo'),(71,'bar');
CREATE TABLE t2 (c int) ENGINE=MyISAM;
INSERT INTO t2 VALUES (1),(2);
CREATE TABLE t3 (d int, e int, KEY(e)) ENGINE=MyISAM;
SELECT * FROM t1 LEFT JOIN t2 LEFT JOIN t3 ON t3.e = t3.d ON 1;
a b c d e
69 foo 1 NULL NULL
71 bar 1 NULL NULL
69 foo 2 NULL NULL
71 bar 2 NULL NULL
SET optimizer_switch = 'not_null_range_scan=on';
SELECT * FROM t1 LEFT JOIN t2 LEFT JOIN t3 ON t3.e = t3.d ON 1;
a b c d e
69 foo 1 NULL NULL
71 bar 1 NULL NULL
69 foo 2 NULL NULL
71 bar 2 NULL NULL
DROP TABLE t1, t2, t3;
set @@optimizer_switch=@save_optimizer_switch;
End of 10.5 tests

36
mysql-test/main/empty_table.test
View file

@ -21,4 +21,38 @@ drop table t1;
select * from t2;
show status like "Empty_queries";
# End of 4.1 tests
--echo # End of 4.1 tests
--echo #
--echo # MDEV-30333 Wrong result with not_null_range_scan and LEFT JOIN with empty table
--echo #
set @save_optimizer_switch=@@optimizer_switch;
CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM;
INSERT INTO t1 (b) VALUES (1),(2);
CREATE TABLE t2 (c INT) ENGINE=MyISAM;
SET optimizer_switch= 'not_null_range_scan=off'; # Default
explain extended SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
SET optimizer_switch = 'not_null_range_scan=on';
explain extended SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
flush tables;
SELECT b FROM t1 LEFT JOIN t2 ON t2.c = a WHERE a IS NULL ORDER BY b;
drop table t1,t2;
--echo # Second test in MDEV-30333
CREATE TABLE t1 (a int, b varchar(10)) ENGINE=MyISAM;
INSERT INTO t1 VALUES (69,'foo'),(71,'bar');
CREATE TABLE t2 (c int) ENGINE=MyISAM;
INSERT INTO t2 VALUES (1),(2);
CREATE TABLE t3 (d int, e int, KEY(e)) ENGINE=MyISAM;
SELECT * FROM t1 LEFT JOIN t2 LEFT JOIN t3 ON t3.e = t3.d ON 1;
SET optimizer_switch = 'not_null_range_scan=on';
SELECT * FROM t1 LEFT JOIN t2 LEFT JOIN t3 ON t3.e = t3.d ON 1;
DROP TABLE t1, t2, t3;
set @@optimizer_switch=@save_optimizer_switch;
--echo End of 10.5 tests

6
sql/sql_select.cc
View file

@ -29683,7 +29683,6 @@ void JOIN::make_notnull_conds_for_range_scans()
{
DBUG_ENTER("JOIN::make_notnull_conds_for_range_scans");
if (impossible_where ||
!optimizer_flag(thd, OPTIMIZER_SWITCH_NOT_NULL_RANGE_SCAN))
{
@ -29769,7 +29768,6 @@ bool build_notnull_conds_for_range_scans(JOIN *join, Item *cond,
table_map allowed)
{
THD *thd= join->thd;
DBUG_ENTER("build_notnull_conds_for_range_scans");
for (JOIN_TAB *s= join->join_tab;
@ -29777,13 +29775,13 @@ bool build_notnull_conds_for_range_scans(JOIN *join, Item *cond,
{
/* Clear all needed bitmaps to mark found fields */
if ((allowed & s->table->map) &&
!(s->table->map && join->const_table_map))
!(s->table->map & join->const_table_map))
bitmap_clear_all(&s->table->tmp_set);
}
/*
Find all null-rejected fields assuming that cond is null-rejected and
only formulas over tables from 'allowed' are to be taken into account
only formulas over tables from 'allowed' are to be taken into account
*/
if (cond->find_not_null_fields(allowed))
DBUG_RETURN(true);