On 2013-01-25 11:51:33 -0500, Tom Lane wrote: > Alvaro Herrera <alvhe...@2ndquadrant.com> writes: > > 2. for other tables, consider floor(log(size)). This makes tables of > > sizes in the same ballpark be considered together. > > > 3. For tables of similar size, consider > > (n_dead_tuples - threshold) / threshold. > > "threshold" is what gets calculated as the number of tuples over which > > a table is considered for vacuuming. This number, then, is a relative > > measure of how hard is vacuuming needed. > > The floor(log(size)) part seems like it will have rather arbitrary > behavioral shifts when a table grows just past a log boundary. Also, > I'm not exactly sure whether you're proposing smaller tables first or > bigger tables first, nor that either of those orderings is a good thing.
That seems dubious to me as well. > I think sorting by just age(relfrozenxid) for for-wraparound tables, and > just the n_dead_tuples measurement for others, is probably reasonable > for now. If we find out that has bad behaviors then we can look at how > to fix them, but I don't think we have enough understanding yet of what > the bad behaviors might be. If we want another ordering criterion than that it might be worth thinking about something like n_dead_tuples/relpages to make sure that small tables with a high dead tuples ratio get vacuumed in time. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
