MDEV-9462: Out of memory using explain on 2 empty tables

Fixed adding derived tables items to outer one.

sql/sql_lex.h

@@ -1060,6 +1060,13 @@ class st_select_lex: public st_select_lex_node
   index_clause_map current_index_hint_clause;
   /* a list of USE/FORCE/IGNORE INDEX */
   List<Index_hint> *index_hints;
+
+public:
+  inline void add_where_field(st_select_lex *sel)
+  {
+    DBUG_ASSERT(this != sel);
+    select_n_where_fields+= sel->select_n_where_fields;
+  }
 };
 typedef class st_select_lex SELECT_LEX;
 

sql/sql_view.cc

@@ -1523,8 +1523,7 @@ bool mysql_make_view(THD *thd, File_parser *parser, TABLE_LIST *table,
 
       /* Fields in this view can be used in upper select in case of merge.  */
       if (table->select_lex)
-        table->select_lex->select_n_where_fields+=
-          lex->select_lex.select_n_where_fields;
+        table->select_lex->add_where_field(&lex->select_lex);
     }
     /*
       This method has a dependency on the proper lock type being set,

sql/sql_yacc.yy

@@ -9872,15 +9872,6 @@ table_factor:
               sel->add_joined_table($$);
               lex->pop_context();
               lex->nest_level--;
-              /*
-                Fields in derived table can be used in upper select in
-                case of merge. We do not add HAVING fields because we do
-                not merge such derived. We do not add union because
-                also do not merge them
-              */
-              if (!sel->next_select())
-                $2->select_n_where_fields+=
-                  sel->select_n_where_fields;
             }
             /*else if (($3->select_lex &&
                       $3->select_lex->master_unit()->is_union() &&
@@ -9901,6 +9892,15 @@ table_factor:
                  nest_level is the same as in the outer query */
               $$= $3;
             }
+            /*
+              Fields in derived table can be used in upper select in
+              case of merge. We do not add HAVING fields because we do
+              not merge such derived. We do not add union because
+              also do not merge them
+            */
+            if ($$ && $$->derived &&
+                !$$->derived->first_select()->next_select())
+              $$->select_lex->add_where_field($$->derived->first_select());
           }
         ;