MDEV-4593: p_s: crash in simplify_joins with delete using subselect from view

mysql_derived_merge_for_insert() should not be called for views or derived tables which are not put (directly or via other views) in main SELECT_LEX "join list".

mysql-test/r/view.result

@@ -4651,6 +4651,18 @@ a
 1
 drop view v1;
 drop table t1,t2;
+#
+# MDEV-4593: p_s: crash in simplify_joins with delete using subselect
+# from view
+#
+create table `t1`(`a` int);
+create table `t2`(`a` int);
+create or replace view `v1` as select `a` from `t1`;
+prepare s from "delete  from `t2` order by (select 1 from `v1`)";
+execute s;
+deallocate prepare s;
+drop view v1;
+drop tables t1,t2;
 # -----------------------------------------------------------------
 # -- End of 5.3 tests.
 # -----------------------------------------------------------------

mysql-test/t/view.test

@@ -4596,6 +4596,20 @@ WHERE a = alias.a );
 drop view v1;
 drop table t1,t2;
 
+--echo #
+--echo # MDEV-4593: p_s: crash in simplify_joins with delete using subselect
+--echo # from view
+--echo #
+
+create table `t1`(`a` int);
+create table `t2`(`a` int);
+create or replace view `v1` as select `a` from `t1`;
+prepare s from "delete  from `t2` order by (select 1 from `v1`)";
+execute s;
+deallocate prepare s;
+drop view v1;
+drop tables t1,t2;
+
 --echo # -----------------------------------------------------------------
 --echo # -- End of 5.3 tests.
 --echo # -----------------------------------------------------------------

sql/sql_derived.cc

@@ -83,7 +83,16 @@ mysql_handle_derived(LEX *lex, uint phases)
 	 sl && !res;
 	 sl= sl->next_select_in_list())
     {
-      for (TABLE_LIST *cursor= sl->get_table_list();
+      TABLE_LIST *cursor= sl->get_table_list();
+      /*
+        DT_MERGE_FOR_INSERT is not needed for views/derived tables inside
+        subqueries. Views and derived tables of subqueries should be
+        processed normally.
+      */
+      if (phases == DT_MERGE_FOR_INSERT &&
+          cursor && cursor->top_table()->select_lex != &lex->select_lex)
+        continue;
+      for (;
 	   cursor && !res;
 	   cursor= cursor->next_local)
       {