Bug #28687: Search fails on '0000-00-00' date after sql_mode change

When doing indexed search the server constructs a key image for 
faster comparison to the stored keys. While doing that it must not
perform (and stop if they fail) the additional date checks that can 
be turned on by the SQL mode because there already may be values in 
the table that don't comply with the error checks.
Fixed by ignoring these SQL mode bits while making the key image.

mysql-test/r/type_date.result

@@ -175,4 +175,43 @@ EXPLAIN SELECT COUNT(*) FROM t1 WHERE a = NOW();
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	Using where
 DROP TABLE t1;
+CREATE TABLE t1 (a DATE);
+CREATE TABLE t2 (a DATE);
+CREATE INDEX i ON t1 (a);
+INSERT INTO t1 VALUES ('0000-00-00'),('0000-00-00');
+INSERT INTO t2 VALUES ('0000-00-00'),('0000-00-00');
+SELECT * FROM t1 WHERE a = '0000-00-00';
+a
+0000-00-00
+0000-00-00
+SELECT * FROM t2 WHERE a = '0000-00-00';
+a
+0000-00-00
+0000-00-00
+SET SQL_MODE=TRADITIONAL;
+EXPLAIN SELECT * FROM t1 WHERE a = '0000-00-00';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	i	i	4	const	1	Using where; Using index
+Warnings:
+Warning	1292	Incorrect date value: '0000-00-00' for column 'a' at row 1
+Warning	1292	Incorrect date value: '0000-00-00' for column 'a' at row 1
+SELECT * FROM t1 WHERE a = '0000-00-00';
+a
+0000-00-00
+0000-00-00
+Warnings:
+Warning	1292	Incorrect date value: '0000-00-00' for column 'a' at row 1
+Warning	1292	Incorrect date value: '0000-00-00' for column 'a' at row 1
+Warning	1292	Incorrect date value: '0000-00-00' for column 'a' at row 1
+SELECT * FROM t2 WHERE a = '0000-00-00';
+a
+0000-00-00
+0000-00-00
+Warnings:
+Warning	1292	Incorrect date value: '0000-00-00' for column 'a' at row 1
+Warning	1292	Incorrect date value: '0000-00-00' for column 'a' at row 1
+INSERT INTO t1 VALUES ('0000-00-00');
+ERROR 22007: Incorrect date value: '0000-00-00' for column 'a' at row 1
+SET SQL_MODE=DEFAULT;
+DROP TABLE t1,t2;
 End of 5.0 tests

mysql-test/t/type_date.test

@@ -170,4 +170,24 @@ EXPLAIN SELECT COUNT(*) FROM t1 WHERE a = NOW();
 
 DROP TABLE t1;
 
+#
+# Bug #28687: Search fails on '0000-00-00' date after sql_mode change
+#
+
+CREATE TABLE t1 (a DATE);
+CREATE TABLE t2 (a DATE);
+CREATE INDEX i ON t1 (a);
+INSERT INTO t1 VALUES ('0000-00-00'),('0000-00-00');
+INSERT INTO t2 VALUES ('0000-00-00'),('0000-00-00');
+SELECT * FROM t1 WHERE a = '0000-00-00';
+SELECT * FROM t2 WHERE a = '0000-00-00';
+SET SQL_MODE=TRADITIONAL;
+EXPLAIN SELECT * FROM t1 WHERE a = '0000-00-00';
+SELECT * FROM t1 WHERE a = '0000-00-00';
+SELECT * FROM t2 WHERE a = '0000-00-00';
+--error ER_TRUNCATED_WRONG_VALUE
+INSERT INTO t1 VALUES ('0000-00-00');
+SET SQL_MODE=DEFAULT;
+DROP TABLE t1,t2;
+
 --echo End of 5.0 tests

sql/item.cc

@@ -938,9 +938,12 @@ int Item::save_in_field_no_warnings(Field *field, bool no_conversions)
   int res;
   THD *thd= field->table->in_use;
   enum_check_fields tmp= thd->count_cuted_fields;
+  ulong sql_mode= thd->variables.sql_mode;
+  thd->variables.sql_mode&= ~(MODE_NO_ZERO_IN_DATE | MODE_NO_ZERO_DATE);
   thd->count_cuted_fields= CHECK_FIELD_IGNORE;
   res= save_in_field(field, no_conversions);
   thd->count_cuted_fields= tmp;
+  thd->variables.sql_mode= sql_mode;
   return res;
 }