Changes between 5.0.40 and 5.0.46

Hi All,

Not sure if this is the correct place to ask this, and it is a fairly ahh...'low priority' question anyway. However, it sparked my interest. I was recently testing a pre-production setup with MySQL 5.0.46 + the patch for bug #30287. I was testing it against version 5.0.40 and noticed something odd. On the following query: SELECT DISTINCT m.*, r.*, u.name, u.uid FROM cvs_messages m INNER JOIN cvs_repositories r ON m.rid = r.rid INNER JOIN users u ON m.uid = u.uid ORDER BY m.created DESC LIMIT 36790, 10;

The two versions had wildly different status outputs for the read_key and read_first handlers. Below is an example diff between the old and new status outputs:
-| Handler_read_first | 77413 |
-| Handler_read_key | 195287 |

+| Handler_read_first                | 34           | 
+| Handler_read_key                  | 38691        | 

This translates into far fewer innodb read requests:

-| Innodb_buffer_pool_read_requests  | 489063       | 

+| Innodb_buffer_pool_read_requests  | 175821       | 

Sooo, clearly I'm not complaining...but is this a known improvement? The query plan is the same for both versions, but it seems like the new one is not doing a full index scan.

-- 
Narayan Newton


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