fixed MDEV-568: Wrong result for a hash index look-up if the index is unique and the key is NULL

Check ability of index to be NULL as it made in MyISAM. UNIQUE with NULL could have several NULL entries so we have to continue even if ve have found a row.

1 files changed, 19 insertions, 0 deletions

diff --git a/mysql-test/r/heap_hash.result b/mysql-test/r/heap_hash.result
index bae49af462f..a0872fb09c5 100644
--- a/mysql-test/r/heap_hash.result
+++ b/mysql-test/r/heap_hash.result
@@ -382,3 +382,22 @@ INSERT INTO t1 VALUES('A ', 'A ');
 ERROR 23000: Duplicate entry 'A -A ' for key 'key1'
 DROP TABLE t1;
 End of 5.0 tests
+#
+# MDEV-568 (AKA LP BUG#1007981, AKA MySQL bug#44771)
+# Wrong result for a hash index look-up if the index is unique and
+# the key is NULL
+#
+CREATE TABLE t1 ( pk INT PRIMARY KEY, val INT, UNIQUE KEY USING HASH(val)) ENGINE=MEMORY;
+INSERT INTO t1 VALUES (1, NULL);
+INSERT INTO t1 VALUES (2, NULL);
+INSERT INTO t1 VALUES (3, 1);
+INSERT INTO t1 VALUES (4, NULL);
+EXPLAIN SELECT * FROM t1 WHERE val IS NULL;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	val	val	5	const	1	Using where
+SELECT * FROM t1 WHERE val IS NULL;
+pk	val
+4	NULL
+2	NULL
+1	NULL
+drop table t1;