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Re: How do FKs work?

From: "Marc G(dot) Fournier" <scrappy(at)postgresql(dot)org>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-sql(at)postgresql(dot)org
Subject: Re: How do FKs work?
Date: 2004-10-10 00:43:50
Message-ID: 20041009214318.V54093@ganymede.hub.org (view raw or flat)
Thread:
Lists: pgsql-sql
On Sat, 9 Oct 2004, Tom Lane wrote:

> "Marc G. Fournier" <scrappy(at)hub(dot)org> writes:
>> Have a table with two FKs on it ... 2 different fields in the table point
>> to the same field in another table ...
>
>> When I do an 'EXPLAIN ANALYZE DELETE FROM table WHERE field = #;', it
>> never comes back ... or, at lesat, takes a *very* long time ...
>
> Do you have indexes on the referencing columns?  Are they exactly the
> same datatype as the referenced column?  You can get really awful plans
> for the FK-checking queries if not.

Yup, that was my first thought ... running SELECT's joining the two tables 
on the FK fields shows indices being used, and fast times ...

----
Marc G. Fournier           Hub.Org Networking Services (http://www.hub.org)
Email: scrappy(at)hub(dot)org           Yahoo!: yscrappy              ICQ: 7615664

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