On Thu, Jun 30, 2011 at 1:53 AM, Samuel Gendler
<sgendler@ideasculptor.com> wrote:
If I could figure out either a query structure or an index structure which will force the fast query plan, I'd be much happier. So that is what I am looking for - an explanation of how I might convince the planner to always use the fast plan.
For the record, "set enable_nestloop=false" does force a more effective plan when using the 'slow' query. It is not quite identical in structure - it materializes the other side of the query, resulting in about 10% less performance - but it is close enough that I'm tempted to disable nestloop whenever I run the query in the hope that it will prevent the planner from switching to the really awful plan. I know that's kind of a drastic measure, so hopefully someone out there will suggest a config fix which accomplishes the same thing without requiring special handling for this query, but at least it works (for now).
Incidentally, upgrading to 9.0.x is not out of the question if it is believed that doing so might help here. I'm only running 8.4 because I've got another project in production on 8.4 and I don't want to have to deal with running both versions on my development laptop. But that's a pretty weak reason for not upgrading, I know.
--sam