"Josh Berkus" <[EMAIL PROTECTED]> writes: > On Wednesday 30 May 2007 15:51, Josh Berkus wrote: >> I now have a simple test case which shows significant performance >> degradation on 8.3devel for a specific query, apparenly due to an >> unnecessary call to Top-N sort. I've tried to forward the test case to >> the lists but the package is 3.5m, so I'm putting it on pgFoundry >> instead:
How recently did you check out your 8.3 tree? When I run it I get a bitmap index scan which I think might mean you're suffering from the same problem Tom found and fixed a few days ago. The planner is finding the bitmap index scan with the sort is the best possible plan but then discarding that option later leaving it with a suboptimal choice. The exact manifestation is somewhat different from what other people saw. iirc they saw sequential scans when there was an index scan available. But I suspect it's the same thing going on. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 7: You can help support the PostgreSQL project by donating at http://www.postgresql.org/about/donate
