On Sat, Jun 6, 2009 at 3:44 PM, Tom Lane<t...@sss.pgh.pa.us> wrote: > I complained a couple days ago that in HEAD, vacuum is putting > very bogus values into pg_class.reltuples for indexes: > http://archives.postgresql.org/pgsql-bugs/2009-06/msg00037.php > > After looking through the code a bit, I've confirmed my prior guess that > this is caused by the partial-vacuum patch. The number that's being > used is the number of live tuples found on the pages that were actually > scanned. There's a kluge in there to keep from storing this number as > the relation's own reltuples, but the implications for indexes were not > considered. The index AMs generally assume that what they're told in > IndexVacuumInfo.num_heap_tuples can be trusted, and that's not true > anymore. > > I think probably the only workable solution for 8.4 is to use the prior > value of the relation's reltuples field as num_heap_tuples when we have > not scanned the whole heap. This will effectively mean that index > reltuples values don't change either in a partial vacuum.
Am I wrong to be frightened by the implications of updating this value only once in a blue moon? Doesn't this have the potential to result in really bad plans? Do we have any reasonable manual way of forcing VACUUM to scan the entire heap? ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
