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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
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36
mysql-test/main/empty_table.test
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@ -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