Bug#30020: Insufficient check led to a wrong info provided by the

information schema table.

The get_schema_views_record() function fills records in the view table of
the informations schema with data about given views. Among other info
the is_updatable flag is set. But the check whether the view is updatable or
not wasn't covering all cases thus sometimes providing wrong info.
This might led to a user confusion.

Now the get_schema_views_record function additionally calls to the 
view->can_be_merge() function to find out whether the view can be updated or
not.


mysql-test/t/view.test:
  Added a test case for the bug#30020: Insufficient check led to a wrong info
  provided by the information schema table.
mysql-test/r/view.result:
  Added a test case for the bug#30020: Insufficient check led to a wrong info
  provided by the information schema table.
sql/sql_show.cc:
  Bug#30020: Insufficient check led to a wrong info provided by the
  information schema table.
  Now the get_schema_views_record function additionally calls to the 
  view->can_be_merge() function to find out whether the view can be updated or
  not.

mysql-test/r/view.result

@@ -3547,4 +3547,19 @@ a	b
 6	6
 DROP VIEW v1;
 DROP TABLE t1,t2,t3;
+create table t1 (i int);
+insert into t1 values (1), (2), (1), (3), (2), (4);
+create view v1 as select distinct i from t1;
+select * from v1;
+i
+1
+2
+3
+4
+select table_name, is_updatable from information_schema.views 
+where table_name = 'v1';
+table_name	is_updatable
+v1	NO
+drop view v1;
+drop table t1;
 End of 5.0 tests.

mysql-test/t/view.test

@@ -3402,5 +3402,18 @@ SELECT t.person_id AS a, t.person_id AS b FROM v1 t WHERE t.person_id=6;
 DROP VIEW v1;
 DROP TABLE t1,t2,t3;
 
+#
+# Bug#30020: Insufficient check led to a wrong info provided by the
+#            information schema table.
+#
+create table t1 (i int);
+insert into t1 values (1), (2), (1), (3), (2), (4);
+create view v1 as select distinct i from t1;
+select * from v1;
+select table_name, is_updatable from information_schema.views 
+   where table_name = 'v1';
+drop view v1;
+drop table t1;
+
 --echo End of 5.0 tests.
 

sql/sql_show.cc

@@ -3211,7 +3211,7 @@ static int get_schema_views_record(THD *thd, TABLE_LIST *tables,
       Item *item;
       Item_field *field;
       /*
-        chech that at least one coulmn in view is updatable
+        check that at least one column in view is updatable
       */
       while ((item= it++))
       {
@@ -3222,6 +3222,8 @@ static int get_schema_views_record(THD *thd, TABLE_LIST *tables,
           break;
         }
       }
+      if (updatable_view && !tables->view->can_be_merged())
+        updatable_view= 0;
     }
     if (updatable_view)
       table->field[5]->store(STRING_WITH_LEN("YES"), cs);