2011/10/3 Nowak Michał <michal.no...@me.com>: > Some info about data distrubution: > > a9-dev=> select min(id) from records; > min > -------- > 190830 > (1 row) > > a9-dev=> select min(id), max(id) from records where > source_id='http://ebuw.uw.edu.pl/dlibra/oai-pmh-repository.xml'; > min | max > ---------+--------- > 1105217 | 3811326 > (1 row) > a9-dev=> select min(id), max(id) from records where > source_id='http://www.wbc.poznan.pl/dlibra/oai-pmh-repository.xml'; > min | max > ---------+--------- > 1544991 | 3811413 > (1 row)
PG assumes that the "wbc.poznan.pl" rows are all over the range of ids, which seems not to be the case. There is no sense of cross-column correlation in the planner currently. You are going to have to resort to some more or less cute hacks, like making an index on (source_id, id - 1) and doing "... order by source_id, id - 1" . Greetings Marcin Mańk -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
