From: John Fabiani <johnf@jfcomputer.com>
To: pgsql-sql@postgresql.org
Subject: Re: foreign key is it a real key
Date: Mon, 13 Feb 2012 09:30:38 -0800
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On Monday, February 13, 2012 04:50:47 PM Andreas Kretschmer wrote:
> 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

Thanks
Johnf