"Angva" <angvaw@xxxxxxxxx> writes: > Our company's application runs searches with "like" where clauses, for > example: "where id like '38F20A%'". This query once ran in under 10 ms, > but since upgrading from 8.1.3 to 8.2.0, it now takes about 500 ms to > run. The problem appears to be that the planner does not want to use an > index since the upgrade, for "like" queries. > We experimented with planner cost constants, and we even tried setting > enable_seqscan to false. A seq scan was done every time. If it won't do it even with seqscan off, then it can't, which most likely means that you mistakenly picked a non-C locale for the new installation. You can either fix that (requiring re-initdb :-() or provide a "pattern_ops" index that's not subject to locale oddities. Non-C locales tend to impose a sort ordering that's not suited for LIKE pattern matching. See http://www.postgresql.org/docs/8.2/static/indexes-opclass.html regards, tom lane
