"Simon Riggs" <[EMAIL PROTECTED]> writes: > How much memory would it save during VACUUM on a 1 billion row table > with 200 million dead rows? Would that reduce the number of cycles a > normal non-interrupted VACUUM would perform?
It would depend on how many dead tuples you have per-page. If you have a very large table with only one dead tuple per page then it might even be larger. But in the usual case it would be smaller. Also note that it would have to be non-lossy. My only objection to this idea, and it's not really an objection at all, is that I think we want to head in the direction of making indexes cheaper to scan and doing the index scan phase more often. That reduces the need for multiple concurrent vacuums and makes the problem of busy tables getting starved less of a concern. That doesn't mean there's any downside to making the dead tuple list take less memory but I think the upside is limited. As we optimize our index representations with GII and bitmapped indexes scanning them gets easier and easier anyways. And you don't really want to wait too long before you get the benefit of the recovered space in the table. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
