Re: Slow indexscan

On Jun 20, 2007, at 9:02 , Mikko Partio wrote:

> Relevant facts:
> pg version 7.3.4 (yeah very old, we are upgrading asap)

There have been many performance improvements—not to mention security
and data-eating bug fixes—since then. Upgrading should be one of your
highest priorities. And it may even fix the issue at hand!

> Index Scan using tbl_20070601_pkey on tbl_20070601 t1
> (cost=0.00..365.13rows=13 width=137) (actual time=
> 120.83..10752.64 rows=539 loops=1)

Something appears a bit off with your index, or at least the
statistics Postgres is using to estimate it. It's estimating that the
query will return 13 rows, but you're actually returning 539. Maybe
there's some corruption in the index which is leading to both the
performance issue you're seeing and the statistics issues. Have you
tried REINDEX?

Michael Glaesemann
grzm seespotcode net