allow merging views with subqueries in WHERE clause (BUG#5504)

mysql-test/r/view.result

@@ -1457,3 +1457,42 @@ View	Create View
 v1	CREATE ALGORITHM=TEMPTABLE VIEW `test`.`v1` AS select `test`.`t1`.`a` AS `a` from `test`.`t1`
 drop view v1;
 drop table t1;
+create table t1 (s1 int);
+create table t2 (s1 int);
+create view v2 as select * from t2 where s1 in (select s1 from t1);
+insert into v2 values (5);
+insert into t1 values (5);
+select * from v2;
+s1
+5
+update v2 set s1 = 0;
+select * from v2;
+s1
+select * from t2;
+s1
+0
+alter view v2 as select * from t2 where s1 in (select s1 from t1) with check option;
+insert into v2 values (5);
+update v2 set s1 = 1;
+ERROR HY000: CHECK OPTION failed 'test.v2'
+insert into t1 values (1);
+update v2 set s1 = 1;
+select * from v2;
+s1
+1
+select * from t2;
+s1
+0
+1
+prepare stmt1 from "select * from v2;";
+execute stmt1;
+s1
+1
+insert into t1 values (0);
+execute stmt1;
+s1
+0
+1
+deallocate prepare stmt1;
+drop view v2;
+drop table t1, t2;

mysql-test/t/view.test

@@ -1421,3 +1421,33 @@ alter algorithm=temptable view v1 as select * from t1;
 show create view v1;
 drop view v1;
 drop table t1;
+
+#
+# updating view with subquery in the WHERE clause
+#
+create table t1 (s1 int);
+create table t2 (s1 int);
+create view v2 as select * from t2 where s1 in (select s1 from t1);
+insert into v2 values (5);
+insert into t1 values (5);
+select * from v2;
+update v2 set s1 = 0;
+select * from v2;
+select * from t2;
+# check it with check option
+alter view v2 as select * from t2 where s1 in (select s1 from t1) with check option;
+insert into v2 values (5);
+-- error 1369
+update v2 set s1 = 1;
+insert into t1 values (1);
+update v2 set s1 = 1;
+select * from v2;
+select * from t2;
+# scheck how VIEWs with subqueries work with prepared statements
+prepare stmt1 from "select * from v2;";
+execute stmt1;
+insert into t1 values (0);
+execute stmt1;
+deallocate prepare stmt1;
+drop view v2;
+drop table t1, t2;

sql/item_subselect.h

@@ -109,6 +109,7 @@ class Item_subselect :public Item_result_field
     engine_changed= 1;
     return eng == 0;
   }
+  enum_parsing_place place() { return parsing_place; }
 
   friend class select_subselect;
   friend class Item_in_optimizer;

sql/sql_lex.cc

@@ -1543,8 +1543,9 @@ void st_select_lex::print_limit(THD *thd, String *str)
     st_lex::can_be_merged()
 
   DESCRIPTION
-    We can apply merge algorithm if it is single SELECT view (we do not
-    count SELECTs of underlying views) and we have not grpouping, ordering,
+    We can apply merge algorithm if it is single SELECT view  with
+    subqueries only in WHERE clause (we do not count SELECTs of underlying
+    views, and second level subqueries) and we have not grpouping, ordering,
     HAVING clause, aggregate functions, DISTINCT clause, LIMIT clause and
     several underlying tables.
 
@@ -1558,14 +1559,23 @@ bool st_lex::can_be_merged()
   // TODO: do not forget implement case when select_lex.table_list.elements==0
 
   /* find non VIEW subqueries/unions */
-  uint selects= 0;
-  for (SELECT_LEX *sl= all_selects_list;
-       sl && selects <= 1;
-       sl= sl->next_select_in_list())
-    if (sl->parent_lex == this)
-      selects++;
-
-  return (selects <= 1 &&
+  bool selects_allow_merge= select_lex.next_select() == 0;
+  if (selects_allow_merge)
+  {
+    for (SELECT_LEX_UNIT *unit= select_lex.first_inner_unit();
+         unit;
+         unit= unit->next_unit())
+    {
+      if (unit->first_select()->parent_lex == this &&
+          (unit->item == 0 || unit->item->place() != IN_WHERE))
+      {
+        selects_allow_merge= 0;
+        break;
+      }
+    }
+  }
+
+  return (selects_allow_merge &&
 	  select_lex.order_list.elements == 0 &&
 	  select_lex.group_list.elements == 0 &&
 	  select_lex.having == 0 &&

sql/sql_view.cc

@@ -753,6 +753,20 @@ mysql_make_view(File_parser *parser, TABLE_LIST *table)
       /* Store WHERE clause for post-processing in setup_ancestor */
       table->where= lex->select_lex.where;
 
+      /*
+        Add subqueries units to SELECT in which we merging current view.
+
+        NOTE: we do not support UNION here, so we take only one select
+      */
+      for (SELECT_LEX_UNIT *unit= lex->select_lex.first_inner_unit();
+           unit;
+           unit= unit->next_unit())
+      {
+        SELECT_LEX_NODE *save_slave= unit->slave;
+        unit->include_down(table->select_lex);
+        unit->slave= save_slave; // fix include_down initialisation
+      }
+
       /*
 	This SELECT_LEX will be linked in global SELECT_LEX list
 	to make it processed by mysql_handle_derived(),
@@ -923,8 +937,12 @@ bool check_key_in_view(THD *thd, TABLE_LIST *view)
   uint i, elements_in_view;
   DBUG_ENTER("check_key_in_view");
 
-  if (!view->view ||
-      thd->lex->unit.global_parameters->select_limit == HA_POS_ERROR)
+  /*
+    we do not support updatable UNIONs in VIW, so we can check just limit of
+    LEX::select_lex
+  */
+  if (!view->view || thd->lex->sql_command == SQLCOM_INSERT ||
+      thd->lex->select_lex.select_limit == HA_POS_ERROR)
     DBUG_RETURN(FALSE); /* it is normal table or query without LIMIT */
   table= view->table;
   trans= view->field_translation;