Planner tuning

I have a query here for which postgres chooses a nested loop, for which
it takes ~19s to complete in the worst-case (measured). However, if I
disable nestloops it completes in ~400ms...

It seems pretty obvious that the planner underestimates the cost of
nestloops here, is there some way to tweak this?

This is using PostgreSQL 8.1.4 on x86_64-pc-linux-gnu, compiled by GCC
cc (GCC) 3.3.5 (Debian 1:3.3.5-13)

The server is on some kind of xen domain. I have absolutely no idea what
impact that has for various planner parameters (except that it'll
probably not perform as well as an unxenned server), it may be relevant.

The plans with and w/o nestloops respectively are attached (to prevent
wrapping).

--
Alban Hertroys
alban(at)magproductions(dot)nl

magproductions b.v.

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