On Wed, 2006-05-03 at 10:17 -0400, Tom Lane wrote: > Simon Riggs <[EMAIL PROTECTED]> writes:
> You are optimizing the wrong thing here. If we choose not to mark an > entry dead then we will pay for that omission on every future scan of > the same entry. I don't think that outweighs the (doubtless rare) > situation where we expend an extra page fetch to reload the page. Sounds a familiar conversation, which I shouldn't have raised here. This depends upon whether the pages being accessed are in cache or not, and whether we have sufficient I/O to pay the cost of a write. Reads don't always go to disk, writes always do. I see that its difficult to tell which is which, but that doesn't mean there aren't different cases. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
