Check of temporary tables hiding for query fetched from QC (BUG#6084)

mysql-test/r/query_cache.result:
  hiding real table stored in query cache by temporary table
mysql-test/t/query_cache.test:
  hiding real table stored in query cache by temporary table
sql/sql_cache.cc:
  Check of temporary tables hiding for query fetched from QC
sql/sql_cache.h:
  Key length now stored in table record of query cache

mysql-test/r/query_cache.result

@@ -704,4 +704,17 @@ Qcache_queries_in_cache	1
 unlock table;
 drop table t1,t2;
 set query_cache_wlock_invalidate=default;
+CREATE TABLE t1 (id INT PRIMARY KEY);
+insert into t1 values (1),(2),(3);
+select * from t1;
+id
+1
+2
+3
+create temporary table t1 (a int not null auto_increment
+primary key);
+select * from t1;
+a
+drop table t1;
+drop table t1;
 set GLOBAL query_cache_size=0;

mysql-test/t/query_cache.test

@@ -521,4 +521,16 @@ unlock table;
 drop table t1,t2;
 set query_cache_wlock_invalidate=default;
 
+#
+# hiding real table stored in query cache by temporary table
+#
+CREATE TABLE t1 (id INT PRIMARY KEY);
+insert into t1 values (1),(2),(3);
+select * from t1;
+create temporary table t1 (a int not null auto_increment
+primary key);
+select * from t1;
+drop table t1;
+drop table t1;
+
 set GLOBAL query_cache_size=0;

sql/sql_cache.cc

@@ -971,9 +971,38 @@ Query_cache::send_result_to_client(THD *thd, char *sql, uint query_length)
   for (; block_table != block_table_end; block_table++)
   {
     TABLE_LIST table_list;
-    bzero((char*) &table_list,sizeof(table_list));
+    TABLE *tmptable;
 
     Query_cache_table *table = block_table->parent;
+
+    /*
+      Check that we have not temporary tables with same names of tables
+      of this query. If we have such tables, we will not send data from
+      query cache, because temporary tables hide real tables by which
+      query in query cache was made.
+    */
+    for (tmptable= thd->temporary_tables; tmptable ; tmptable= tmptable->next)
+    {
+      if (tmptable->key_length - 8 == table->key_len() &&
+          !memcmp(tmptable->table_cache_key, table->data(),
+                  table->key_len()))
+      {
+        DBUG_PRINT("qcache",
+                   ("Temporary table detected: '%s.%s'",
+                    table_list.db, table_list.alias));
+        STRUCT_UNLOCK(&structure_guard_mutex);
+        /*
+          We should not store result of this query because it contain
+          temporary tables => assign following wariable to make check
+          faster.
+        */
+        thd->safe_to_cache_query=0;
+        BLOCK_UNLOCK_RD(query_block);
+        DBUG_RETURN(-1);
+      }
+    }
+
+    bzero((char*) &table_list,sizeof(table_list));
     table_list.db = table->db();
     table_list.alias= table_list.real_name= table->table();
     if (check_table_access(thd,SELECT_ACL,&table_list,1))
@@ -2066,6 +2095,7 @@ Query_cache::insert_table(uint key_len, char *key,
     }
     char *db = header->db();
     header->table(db + db_length + 1);
+    header->key_len(key_len);
   }
 
   Query_cache_block_table *list_root = table_block->table(0);

sql/sql_cache.h

@@ -144,10 +144,13 @@ struct Query_cache_query
 struct Query_cache_table
 {
   char *tbl;
+  uint32 key_length;
 
   inline char *db()			     { return (char *) data(); }
   inline char *table()			     { return tbl; }
   inline void table(char *table)	     { tbl = table; }
+  inline uint32 key_len()                    { return key_length; }
+  inline void key_len(uint32 len)            { key_length= len; }
   inline gptr data()
   {
     return (gptr)(((byte*)this)+