Bug#30269 Query cache eats memory

Although the query cache doesn't support retrieval of statements containing
column level access control, it was still possible to cache such statements
thus wasting memory.
  
This patch extends the access control check on the target tables to avoid
caching a statement with column level restrictions. 

Views are excepted and can be cached but only retrieved by super user account.

mysql-test/r/query_cache.result

@@ -1503,10 +1503,11 @@ a	(select count(*) from t2)
 4	0
 drop table t1,t2;
 DROP DATABASE IF EXISTS bug30269;
+FLUSH STATUS;
 CREATE DATABASE bug30269;
 USE bug30269;
 CREATE TABLE test1 (id int, name varchar(23));
-CREATE VIEW view1 AS SELECT id FROM test1;
+CREATE VIEW view1 AS SELECT * FROM test1;
 INSERT INTO test1 VALUES (5, 'testit');
 GRANT SELECT (id) ON TABLE bug30269.test1 TO 'bug30269'@'localhost';
 GRANT SELECT ON TABLE bug30269.view1 TO 'bug30269'@'localhost';
@@ -1515,15 +1516,19 @@ USE bug30269;
 show status like 'Qcache_queries_in_cache';
 Variable_name	Value
 Qcache_queries_in_cache	0
+# Select statement not stored in query cache because of column privileges.
 SELECT id FROM test1 WHERE id>2;
 id
 5
+show status like 'Qcache_queries_in_cache';
+Variable_name	Value
+Qcache_queries_in_cache	0
 SELECT id FROM view1 WHERE id>2;
 id
 5
 show status like 'Qcache_queries_in_cache';
 Variable_name	Value
-Qcache_queries_in_cache	0
+Qcache_queries_in_cache	1
 DROP DATABASE bug30269;
 DROP USER 'bug30269'@'localhost';
 set GLOBAL query_cache_type=default;

mysql-test/t/query_cache.test

@@ -1103,10 +1103,11 @@ disconnect user3;
 --disable_warnings
 DROP DATABASE IF EXISTS bug30269;
 --enable_warnings
+FLUSH STATUS;
 CREATE DATABASE bug30269;
 USE bug30269;
 CREATE TABLE test1 (id int, name varchar(23));
-CREATE VIEW view1 AS SELECT id FROM test1;
+CREATE VIEW view1 AS SELECT * FROM test1;
 INSERT INTO test1 VALUES (5, 'testit');
 GRANT SELECT (id) ON TABLE bug30269.test1 TO 'bug30269'@'localhost';
 GRANT SELECT ON TABLE bug30269.view1 TO 'bug30269'@'localhost';
@@ -1115,7 +1116,9 @@ connect (bug30269, localhost, bug30269,,);
 connection bug30269;
 USE bug30269;
 show status like 'Qcache_queries_in_cache';
+--echo # Select statement not stored in query cache because of column privileges.
 SELECT id FROM test1 WHERE id>2;
+show status like 'Qcache_queries_in_cache';
 SELECT id FROM view1 WHERE id>2;
 show status like 'Qcache_queries_in_cache';
 

sql/sql_cache.cc

@@ -3007,8 +3007,19 @@ Query_cache::process_and_count_tables(THD *thd, TABLE_LIST *tables_used,
       The grant.want_privileges flag was set to 1 in the
       check_grant() function earlier if the TABLE_LIST object
       had any associated column privileges.
+
+      We need to check that the TABLE_LIST object isn't part
+      of a VIEW definition because we want to be able to cache
+      views.
+
+      TODO: Although it is possible to cache views, the privilege
+      check on view tables always fall back on column privileges
+      even if there are more generic table privileges. Thus it isn't
+      currently possible to retrieve cached view-tables unless the
+      client has the super user privileges.
     */
-    if (tables_used->grant.want_privilege)
+    if (tables_used->grant.want_privilege &&
+        tables_used->belong_to_view == NULL)
     {
       DBUG_PRINT("qcache", ("Don't cache statement as it refers to "
                             "tables with column privileges."));