- Make subselect_sj2 testcase more stable

- Better comments

mysql-test/r/subselect_sj2.result

@@ -359,6 +359,10 @@ Canada
 China
 Czech Republic
 drop table t1, t2;
+drop procedure if exists p1;
+drop procedure if exists p2;
+drop procedure if exists p3;
+drop procedure if exists p4;
 CREATE TABLE t1(a INT);
 CREATE TABLE t2(c INT);
 CREATE PROCEDURE p1(v1 int)

mysql-test/r/subselect_sj2_jcl6.result

@@ -363,6 +363,10 @@ Canada
 China
 Czech Republic
 drop table t1, t2;
+drop procedure if exists p1;
+drop procedure if exists p2;
+drop procedure if exists p3;
+drop procedure if exists p4;
 CREATE TABLE t1(a INT);
 CREATE TABLE t2(c INT);
 CREATE PROCEDURE p1(v1 int)

mysql-test/t/subselect_sj2.test

@@ -490,6 +490,12 @@ drop table t1, t2;
 # Bug#33062: subquery in stored routine cause crash
 #
 
+--disable_warnings
+drop procedure if exists p1;
+drop procedure if exists p2;
+drop procedure if exists p3;
+drop procedure if exists p4;
+--enable_warnings
 CREATE TABLE t1(a INT);
 CREATE TABLE t2(c INT);
 

sql/item_subselect.h

@@ -46,6 +46,7 @@ public:
           < child_join->prepare
         < engine->prepare
         *ref= substitution;
+        substitution= NULL;
       < Item_subselect::fix_fields
   */
   Item *substitution;
@@ -390,6 +391,7 @@ public:
     
     We can't remove it altogether as it is used to classify contents in
     join->sj_subselects.
+    jtbm-todo: option 1: let sj_subselects list pairs.
   */
   bool convert_to_semi_join;