Re: Foreign keys and slow insert

I think 21 interns will be enough :)

2005/6/8, Scott Marlowe <smarlowe(at)g2switchworks(dot)com>:
>
> On Wed, 2005-06-08 at 12:39, Dan Black wrote:
> > I've observed that inserts into slave table became slower when I use
> > foreign key than without one.
> > Can it be related to foreign key?
> > And I am interested how much performance of database with foreign
> > keys can be different from performance of database without foreign
> > keys? In other words, how much performance decrease on using foreign
> > keys?
>
> The problem you're seeing is usually caused by adding records to a table
> set that starts out empty, and the planner uses seq scans, and as it
> grows, should switch to random seeks, but doesn't know to, because no
> one has bothered to analyze said tables.
>
> Set up the pg_autovacuum daemon or cron vacuumdb -az to run every so
> often to help that.
>
> On the other hand, foreign keys are never zero cost, so even the most
> efficient implementation is gonna be slower than not using them. Data
> coherency costs, either up front (i.e. in the database doing it) or in
> the back (i.e. hiring 20 summer interns to go through your data and find
> the parts that are bad...) :)
>

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