MDEV-18668 Server crash or ASAN use-after-poison in Item_equal_iterator /

           st_select_lex::pushdown_from_having_into_where upon query
           with impossible WHERE condition

Do not push from HAVING into impossible WHERE

2 files changed, 25 insertions, 0 deletions

diff --git a/mysql-test/main/having_cond_pushdown.result b/mysql-test/main/having_cond_pushdown.result
index 9d2fbcead4e..ef7368bd1fb 100644
--- a/mysql-test/main/having_cond_pushdown.result
+++ b/mysql-test/main/having_cond_pushdown.result
@@ -1906,3 +1906,15 @@ EXPLAIN
 DROP TABLE t1,t2;
 DROP VIEW v1;
 DROP FUNCTION f1;
+#
+# MDEV-18668: pushdown from HAVING into impossible WHERE
+#
+CREATE TABLE t1 (a INT, b INT);
+INSERT INTO t1 VALUES (1,1),(2,2);
+SELECT a FROM t1 WHERE b = 1 AND b = 2 GROUP BY a HAVING a <= 3;
+a
+EXPLAIN
+SELECT a FROM t1 WHERE b = 1 AND b = 2 GROUP BY a HAVING a <= 3;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+DROP TABLE t1;
diff --git a/mysql-test/main/having_cond_pushdown.test b/mysql-test/main/having_cond_pushdown.test
index 2af9d58bc4d..2fbb5708c50 100644
--- a/mysql-test/main/having_cond_pushdown.test
+++ b/mysql-test/main/having_cond_pushdown.test
@@ -473,3 +473,16 @@ eval $no_pushdown explain format=json $query;
 DROP TABLE t1,t2;
 DROP VIEW v1;
 DROP FUNCTION f1;
+
+--echo #
+--echo # MDEV-18668: pushdown from HAVING into impossible WHERE
+--echo #
+
+CREATE TABLE t1 (a INT, b INT);
+INSERT INTO t1 VALUES (1,1),(2,2);
+
+SELECT a FROM t1 WHERE b = 1 AND b = 2 GROUP BY a HAVING a <= 3;
+EXPLAIN
+SELECT a FROM t1 WHERE b = 1 AND b = 2 GROUP BY a HAVING a <= 3;
+
+DROP TABLE t1;