Heikki Linnakangas <heikki.linnakan...@enterprisedb.com> writes: > Greg Stark wrote: >> I wonder if we should switch to keeping reltuplesperpage instead. Then a >> partial vacuum could update it by taking the average number of tuples >> per page forbthe pages it saw. Perhaps adjusting it to the weights >> average between the old value and the new value based on how many pages >> were seen.
> The pages scanned by a partial vacuum isn't a random sample of pages in > the table. That would bias the reltuplesperpage value towards those > pages that are updated more. Yeah ... and it's highly likely that repeatedly-updated pages would have more dead space than never-updated ones, so there'd be a systematic creep towards underestimation of the total tuple count. I think your previous sketch is right: suppress update of reltuples (and relpages) from a partial vacuum scan, and ensure that the analyze phase is allowed to do it instead if it happens during VACUUM ANALYZE. 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