Merge stella.local:/home2/mydev/mysql-5.0-axmrg

into  stella.local:/home2/mydev/mysql-5.1-axmrg

mysql-test/r/query_cache.result

@@ -1654,6 +1654,32 @@ set GLOBAL query_cache_type=default;
 set GLOBAL query_cache_limit=default;
 set GLOBAL query_cache_min_res_unit=default;
 set GLOBAL query_cache_size=default;
+FLUSH STATUS;
+SET GLOBAL query_cache_size=10*1024*1024;
+SET @save_concurrent_insert= @@concurrent_insert;
+SET GLOBAL concurrent_insert= 0;
+CREATE TABLE t1 (c1 INT NOT NULL) ENGINE=MyISAM;
+INSERT INTO t1 (c1) VALUES (1), (2);
+SHOW GLOBAL VARIABLES LIKE 'concurrent_insert';
+Variable_name	Value
+concurrent_insert	0
+SHOW STATUS LIKE 'Qcache_hits';
+Variable_name	Value
+Qcache_hits	0
+SELECT * FROM t1;
+c1
+1
+2
+SELECT * FROM t1;
+c1
+1
+2
+SHOW STATUS LIKE 'Qcache_hits';
+Variable_name	Value
+Qcache_hits	1
+DROP TABLE t1;
+SET GLOBAL concurrent_insert= @save_concurrent_insert;
+SET GLOBAL query_cache_size= default;
 End of 5.0 tests
 CREATE TABLE t1 (a ENUM('rainbow'));
 INSERT INTO t1 VALUES (),(),(),(),();

mysql-test/t/query_cache.test

@@ -1298,6 +1298,25 @@ set GLOBAL query_cache_limit=default;
 set GLOBAL query_cache_min_res_unit=default;
 set GLOBAL query_cache_size=default;
 
+#
+# Bug#33756 - query cache with concurrent_insert=0 appears broken
+#
+FLUSH STATUS;
+SET GLOBAL query_cache_size=10*1024*1024;
+SET @save_concurrent_insert= @@concurrent_insert;
+SET GLOBAL concurrent_insert= 0;
+CREATE TABLE t1 (c1 INT NOT NULL) ENGINE=MyISAM;
+INSERT INTO t1 (c1) VALUES (1), (2);
+#
+SHOW GLOBAL VARIABLES LIKE 'concurrent_insert';
+SHOW STATUS LIKE 'Qcache_hits';
+SELECT * FROM t1;
+SELECT * FROM t1;
+SHOW STATUS LIKE 'Qcache_hits';
+DROP TABLE t1;
+SET GLOBAL concurrent_insert= @save_concurrent_insert;
+SET GLOBAL query_cache_size= default;
+
 --echo End of 5.0 tests
 
 #

storage/myisam/ha_myisam.cc

@@ -2098,6 +2098,7 @@ my_bool ha_myisam::register_query_cache_table(THD *thd, char *table_name,
                                               *engine_callback,
                                               ulonglong *engine_data)
 {
+  DBUG_ENTER("ha_myisam::register_query_cache_table");
   /*
     No call back function is needed to determine if a cached statement
     is valid or not.
@@ -2109,39 +2110,48 @@ my_bool ha_myisam::register_query_cache_table(THD *thd, char *table_name,
   */
   *engine_data= 0;
 
-  /*
-    If a concurrent INSERT has happened just before the currently processed
-    SELECT statement, the total size of the table is unknown.
+  if (file->s->concurrent_insert)
+  {
+    /*
+      If a concurrent INSERT has happened just before the currently
+      processed SELECT statement, the total size of the table is
+      unknown.
 
-    To determine if the table size is known, the current thread's snap shot of
-    the table size with the actual table size are compared.
+      To determine if the table size is known, the current thread's snap
+      shot of the table size with the actual table size are compared.
 
-    If the table size is unknown the SELECT statement can't be cached.
-  */
-  ulonglong actual_data_file_length;
-  ulonglong current_data_file_length;
+      If the table size is unknown the SELECT statement can't be cached.
 
-  /*
-    POSIX visibility rules specify that "2. Whatever memory values a
-    thread can see when it unlocks a mutex <...> can also be seen by any
-    thread that later locks the same mutex". In this particular case,
-    concurrent insert thread had modified the data_file_length in
-    MYISAM_SHARE before it has unlocked (or even locked)
-    structure_guard_mutex. So, here we're guaranteed to see at least that
-    value after we've locked the same mutex. We can see a later value
-    (modified by some other thread) though, but it's ok, as we only want
-    to know if the variable was changed, the actual new value doesn't matter
-  */
-  actual_data_file_length= file->s->state.state.data_file_length;
-  current_data_file_length= file->save_state.data_file_length;
+      When concurrent inserts are disabled at table open, mi_open()
+      does not assign a get_status() function. In this case the local
+      ("current") status is never updated. We would wrongly think that
+      we cannot cache the statement.
+    */
+    ulonglong actual_data_file_length;
+    ulonglong current_data_file_length;
 
-  if (current_data_file_length != actual_data_file_length)
-  {
-    /* Don't cache current statement. */
-    return FALSE;
+    /*
+      POSIX visibility rules specify that "2. Whatever memory values a
+      thread can see when it unlocks a mutex <...> can also be seen by any
+      thread that later locks the same mutex". In this particular case,
+      concurrent insert thread had modified the data_file_length in
+      MYISAM_SHARE before it has unlocked (or even locked)
+      structure_guard_mutex. So, here we're guaranteed to see at least that
+      value after we've locked the same mutex. We can see a later value
+      (modified by some other thread) though, but it's ok, as we only want
+      to know if the variable was changed, the actual new value doesn't matter
+    */
+    actual_data_file_length= file->s->state.state.data_file_length;
+    current_data_file_length= file->save_state.data_file_length;
+
+    if (current_data_file_length != actual_data_file_length)
+    {
+      /* Don't cache current statement. */
+      DBUG_RETURN(FALSE);
+    }
   }
 
   /* It is ok to try to cache current statement. */
-  return TRUE;
+  DBUG_RETURN(TRUE);
 }
 #endif