merge

mysql-test/r/ps.result

@@ -3025,6 +3025,24 @@ Warnings:
 Note	1003	select 1 AS `1` from `test`.`t1` `t2` left join `test`.`t1` on(1) where 1
 DEALLOCATE PREPARE stmt;
 DROP TABLE t1;
+#
+# Bug#54488 crash when using explain and prepared statements with subqueries
+#
+CREATE TABLE t1(f1 INT);
+INSERT INTO t1 VALUES (1),(1);
+PREPARE stmt FROM 'EXPLAIN SELECT 1 FROM t1 WHERE (SELECT (SELECT 1 FROM t1 GROUP BY f1))';
+EXECUTE stmt;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort
+EXECUTE stmt;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort
+DEALLOCATE PREPARE stmt;
+DROP TABLE t1;
 
 End of 5.1 tests.
 

mysql-test/t/ps.test

@@ -3090,6 +3090,17 @@ EXECUTE stmt;
 DEALLOCATE PREPARE stmt;
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#54488 crash when using explain and prepared statements with subqueries
+--echo #
+CREATE TABLE t1(f1 INT);
+INSERT INTO t1 VALUES (1),(1);
+PREPARE stmt FROM 'EXPLAIN SELECT 1 FROM t1 WHERE (SELECT (SELECT 1 FROM t1 GROUP BY f1))';
+EXECUTE stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+DROP TABLE t1;
+
 --echo 
 --echo End of 5.1 tests.
 

sql/item_subselect.cc

@@ -1911,18 +1911,22 @@ int subselect_single_select_engine::exec()
     }
     if (!select_lex->uncacheable && thd->lex->describe && 
         !(join->select_options & SELECT_DESCRIBE) && 
-        join->need_tmp && item->const_item())
+        join->need_tmp)
     {
-      /*
-        Force join->join_tmp creation, because this subquery will be replaced
-        by a simple select from the materialization temp table by optimize()
-        called by EXPLAIN and we need to preserve the initial query structure
-        so we can display it.
-       */
-      select_lex->uncacheable|= UNCACHEABLE_EXPLAIN;
-      select_lex->master_unit()->uncacheable|= UNCACHEABLE_EXPLAIN;
-      if (join->init_save_join_tab())
-        DBUG_RETURN(1);                        /* purecov: inspected */
+      item->update_used_tables();
+      if (item->const_item())
+      {
+        /*
+          Force join->join_tmp creation, because this subquery will be replaced
+          by a simple select from the materialization temp table by optimize()
+          called by EXPLAIN and we need to preserve the initial query structure
+          so we can display it.
+        */
+        select_lex->uncacheable|= UNCACHEABLE_EXPLAIN;
+        select_lex->master_unit()->uncacheable|= UNCACHEABLE_EXPLAIN;
+        if (join->init_save_join_tab())
+          DBUG_RETURN(1);                        /* purecov: inspected */
+      }
     }
     if (item->engine_changed)
     {