From: Andreas Kretschmer <akretschmer@spamfence.net>
To: pgsql-sql@postgresql.org
Subject: Re: foreign key is it a real key
Date: Mon, 13 Feb 2012 16:50:47 +0100
Message-ID: <20120213155047.GA25335@tux> (raw)
In-Reply-To: <5075215.HTHcEtzjPG@linux-12>
References: <5075215.HTHcEtzjPG@linux-12>
John Fabiani <johnf@jfcomputer.com> wrote:
> Hi,
> I have read a few articles and I'm not sure if it's me or the authors but I do
> not believe my question was answered.
>
> If I have table that has a PK and a FK - will the planner use the FK just same
> as it would use the PK? IOW's is a FK also an index used by the planner?
>
> I have a lagacy table that contains a FK constraint (vendor_id -->
> vendor_info). I believe I need an index to improve the performance of a query
> because I'm using the column as part of my join. Explain does not appear to
> use it as an index (instead of a seq scan it uses a hash join). But the table
> all ready has a FK key contraint on the column.
Yes, for large tables you have to create a own index on your fk-column.
Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect. (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly." (unknown)
Kaufbach, Saxony, Germany, Europe. N 51.05082°, E 13.56889°
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-sql@postgresql.org
Cc: akretschmer@spamfence.net
Subject: Re: foreign key is it a real key
In-Reply-To: <20120213155047.GA25335@tux>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox