Fixed LP bug #823826.

The method Item_func_isnull::update_used_tables() erroneously did not
update cached values stored in the fields used_tables_cache and
const_item_cache of the Item_func_isnull objects. As a result the
Item_func_isnull::used_tables() returned wrong bitmaps and, as a
consequence, push-down predicates could be attached to wrong tables.

1 files changed, 24 insertions, 1 deletions

diff --git a/mysql-test/t/derived_view.test b/mysql-test/t/derived_view.test
index 48df49226a4..375a63e47e0 100644
--- a/mysql-test/t/derived_view.test
+++ b/mysql-test/t/derived_view.test
@@ -735,7 +735,30 @@ set optimizer_switch='derived_merge=off';
 EXPLAIN
 SELECT * FROM (SELECT * FROM (SELECT @b) AS t) AS s;
 SELECT * FROM (SELECT * FROM (SELECT @b) AS t) AS s;
-set optimizer_switch=@exit_optimizer_switch;
+set optimizer_switch='derived_merge=on';
+
+--echo #
+--echo # LP bug #823826: view over join + IS NULL in WHERE
+--echo #
+
+CREATE TABLE t1 (a int) ;
+INSERT INTO t1 VALUES (1), (1);
+
+CREATE TABLE t2 (b int) ;
+INSERT INTO t2 VALUES (9), (NULL), (7);
+
+CREATE VIEW v1 AS SELECT * FROM t1,t2;
+
+EXPLAIN
+SELECT * FROM (SELECT * FROM t1,t2) t WHERE b IS NULL;
+SELECT * FROM (SELECT * FROM t1,t2) t WHERE b IS NULL;
+
+EXPLAIN
+SELECT * FROM v1 WHERE b IS NULL;
+SELECT * FROM v1 WHERE b IS NULL;
+
+DROP VIEW v1;
+DROP TABLE t1,t2;
 
 # The following command must be the last one the file 
 set optimizer_switch=@exit_optimizer_switch;