A fix and test case for Bug#6873 "PS, having with subquery, crash

during execute"

mysql-test/r/ps.result

@@ -471,3 +471,14 @@ select @var is null, @var is not null, @var;
 execute stmt using @var, @var, @var;
 ? is null	? is not null	?
 1	0	NULL
+create table t1 (pnum char(3));
+create table t2 (pnum char(3));
+prepare stmt from "select pnum from t2 having pnum in (select 'p1' from t1)";
+execute stmt;
+pnum
+execute stmt;
+pnum
+execute stmt;
+pnum
+deallocate prepare stmt;
+drop table t1, t2;

mysql-test/t/ps.test

@@ -471,3 +471,17 @@ execute stmt using @var, @var, @var;
 set @var=null;
 select @var is null, @var is not null, @var;
 execute stmt using @var, @var, @var;
+
+# 
+# Bug#6873 "PS, having with subquery, crash during execute"
+# check that if we modify having subtree, we update JOIN->having pointer
+#
+create table t1 (pnum char(3));
+create table t2 (pnum char(3));
+prepare stmt from "select pnum from t2 having pnum in (select 'p1' from t1)";
+execute stmt;
+execute stmt;
+execute stmt;
+deallocate prepare stmt;
+drop table t1, t2;
+

sql/item_subselect.cc

@@ -155,6 +155,8 @@ bool Item_subselect::fix_fields(THD *thd_param, TABLE_LIST *tables, Item **ref)
       // did we changed top item of WHERE condition
       if (unit->outer_select()->where == (*ref))
 	unit->outer_select()->where= substitution; // correct WHERE for PS
+      else if (unit->outer_select()->having == (*ref))
+	unit->outer_select()->having= substitution; // correct HAVING for PS
 
       (*ref)= substitution;
       substitution->name= name;