Heikki Linnakangas <[EMAIL PROTECTED]> writes: > Tom Lane wrote: >> So it seems like we do indeed want to rejigger autovac's rules a bit >> to account for the possibility of wanting to apply vacuum to get >> visibility bits set.
> I'm not too excited about triggering an extra vacuum. As Matthew pointed > out, the point of this patch is to reduce the number of vacuums > required, not increase it. If you're not going to vacuum a table, you > don't care if the bits in the visibility map are set or not. But it's already the case that the bits provide a performance increase to other things besides vacuum. > We could set the PD_ALL_VISIBLE flag more aggressively, outside VACUUMs, > if we want to make the seqscan optimization more effective. For example, > a seqscan could set the flag too, if it sees that all the tuples were > visible, and had the XMIN_COMMITTED and XMAX_INVALID hint bits set. I was wondering whether we could teach heap_page_prune to set the flag without adding any extra tuple visibility checks. A seqscan per se shouldn't be doing this because it doesn't normally call HeapTupleSatifiesVacuum. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers