Re: 7.3.1 New install, large queries are slow

On Wed, Jan 15, 2003 at 10:00:04AM -0800, Roman Fail wrote:
> I have a query that does many joins (including two very big tables)
> which is slow on Postgres. On PGSQL the query takes 19 minutes,

There are three things I can think of right off the bat.

First, the performance of foreign keys is flat-out awful in Postgres.
I suggest avoiding them if you can.

Second, ordering joins explicitly (with the JOIN keyword) constrains
the planner, and may select bad plan. The explain analyse output
was nice, but I didn't see the query, so I can't tell what the plan
maybe ought to be.

Third, I didn't see any suggestion that you'd moved the WAL onto its
own disk. That will mostly help when you are under write load; I
guess it's not a problem here, but it's worth keeping in mind.

A

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