fixed staistic of subquery if outer field resolved in merged view (BUG#5247)

mysql-test/r/view.result:
  problem with used_tables() of outer reference resolved in VIEW
mysql-test/t/view.test:
  problem with used_tables() of outer reference resolved in VIEW
sql/item.cc:
  fixed staistic of subquery if outer field resolved in merged view

mysql-test/r/view.result

@@ -1230,3 +1230,11 @@ c
 
 drop view v;
 drop table t;
+create table t1 (a int, b int);
+insert into t1 values (1,2), (1,3), (2,4), (2,5), (3,10);
+create view v1(c) as select a+1 from t1 where b >= 4;
+select c from v1 where exists (select * from t1 where a=2 and b=c);
+c
+4
+drop view v1;
+drop table t1;

mysql-test/t/view.test

@@ -1178,3 +1178,13 @@ insert into v
 select * from v;
 drop view v;
 drop table t;
+
+#
+# problem with used_tables() of outer reference resolved in VIEW
+#
+create table t1 (a int, b int);
+insert into t1 values (1,2), (1,3), (2,4), (2,5), (3,10);
+create view v1(c) as select a+1 from t1 where b >= 4;
+select c from v1 where exists (select * from t1 where a=2 and b=c);
+drop view v1;
+drop table t1;

sql/item.cc

@@ -1302,11 +1302,21 @@ bool Item_field::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
 					 table_list, ref,
 					 0, 1)) != not_found_field)
 	  {
-	    if (tmp && tmp != view_ref_found)
-	    {
-	      prev_subselect_item->used_tables_cache|= tmp->table->map;
-	      prev_subselect_item->const_item_cache= 0;
-	    }
+	    if (tmp)
+            {
+              if (tmp != view_ref_found)
+              {
+                prev_subselect_item->used_tables_cache|= tmp->table->map;
+                prev_subselect_item->const_item_cache= 0;
+              }
+              else
+              {
+                prev_subselect_item->used_tables_cache|=
+                  (*ref)->used_tables();
+                prev_subselect_item->const_item_cache&=
+                  (*ref)->const_item();
+              }
+            }
 	    break;
 	  }
 	  if (sl->resolve_mode == SELECT_LEX::SELECT_MODE &&
@@ -2029,11 +2039,21 @@ bool Item_ref::fix_fields(THD *thd, TABLE_LIST *tables, Item **reference)
 				       table_list, reference,
 				       0, 1)) != not_found_field)
 	{
-	  if (tmp && tmp != view_ref_found)
-	  {
-	    prev_subselect_item->used_tables_cache|= tmp->table->map;
-	    prev_subselect_item->const_item_cache= 0;
-	  }
+          if (tmp)
+          {
+            if (tmp != view_ref_found)
+            {
+              prev_subselect_item->used_tables_cache|= tmp->table->map;
+              prev_subselect_item->const_item_cache= 0;
+            }
+            else
+            {
+              prev_subselect_item->used_tables_cache|=
+                (*reference)->used_tables();
+              prev_subselect_item->const_item_cache&=
+                (*reference)->const_item();
+            }
+          }
 	  break;
 	}