MDEV-5284 Assertion `!(*expr)->fixed' fails in replace_where_subcondition with IN suquery

mysql-test/r/subselect_debug.result

@@ -11,3 +11,10 @@ REVERSE(EXISTS(SELECT RAND() FROM t1))
 0
 SET GLOBAL debug=@orig_debug;
 DROP TABLE t1;
+create table t1 (i int);
+insert into t1 values (1),(2);
+select * from t1 where (i < 200 or i = 300) and i in (select i from t1);
+i
+1
+2
+drop table t1;

mysql-test/t/subselect_debug.test

@@ -15,3 +15,13 @@ SELECT SUM(EXISTS(SELECT RAND() FROM t1)) FROM t1;
 SELECT REVERSE(EXISTS(SELECT RAND() FROM t1));
 SET GLOBAL debug=@orig_debug;
 DROP TABLE t1;
+
+#
+# MDEV-5284 Assertion `!(*expr)->fixed' fails in replace_where_subcondition with IN suquery
+#
+
+create table t1 (i int);
+insert into t1 values (1),(2);
+select * from t1 where (i < 200 or i = 300) and i in (select i from t1);
+drop table t1;
+

sql/opt_subselect.cc

@@ -420,9 +420,7 @@ Currently, solution #2 is implemented.
 
 static
 bool subquery_types_allow_materialization(Item_in_subselect *in_subs);
-static bool replace_where_subcondition(JOIN *join, Item **expr, 
-                                       Item *old_cond, Item *new_cond,
-                                       bool do_fix_fields);
+static bool replace_where_subcondition(JOIN *, Item **, Item *, Item *, bool);
 static int subq_sj_candidate_cmp(Item_in_subselect* el1, Item_in_subselect* el2,
                                  void *arg);
 static bool convert_subq_to_sj(JOIN *parent_join, Item_in_subselect *subq_pred);
@@ -1293,7 +1291,7 @@ static bool replace_where_subcondition(JOIN *join, Item **expr,
       }
       else if (item->type() == Item::COND_ITEM)
       {
-        DBUG_ASSERT(!(*expr)->fixed);
+        DBUG_ASSERT(!do_fix_fields || !(*expr)->fixed);
         replace_where_subcondition(join, li.ref(),
                                    old_cond, new_cond,
                                    do_fix_fields);