From: Tom Lane <tgl@sss.pgh.pa.us>
To: Brian Fehrle <brianf@consistentstate.com>
cc: pgsql-performance@postgresql.org
Subject: Re: View with and without ::text casting performs differently.
In-reply-to: <5229097C.4070401@consistentstate.com>
References: <5229097C.4070401@consistentstate.com>
Comments: In-reply-to Brian Fehrle <brianf@consistentstate.com>
 message dated "Thu, 05 Sep 2013 16:45:16 -0600"
Date: Thu, 05 Sep 2013 19:50:18 -0400
Message-ID: <1960.1378425018@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-performance-owner@postgresql.org

Brian Fehrle <brianf@consistentstate.com> writes:
> I have a view, that when created with our create statement works 
> wonderfully, a query on the view with a standard where clause that 
> narrows the result to a single row performs in under a single ms. 
> However, when we export this view and re-import it (dump and restore of 
> the database, which happens often), the exported version of the view has 
> been modified by Postgres to include various typecasting of some columns 
> to text.

This is normal (varchar doesn't actually have any operations of its own).

> All columns that it typecasts to text are varchar(20), so there is 
> nothing wrong in what it's doing there. However, with the view 
> definition including the ::text casting, the query planner changes and 
> it goes into a nested loop, taking a query from <1ms to over ten minutes.

I rather doubt that the now-explicit-instead-of-implicit casts have much
to do with that.  It seems more likely that you forgot to re-ANALYZE in
the new database, or there are some different planner settings, or
something along that line.

			regards, tom lane


-- 
Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance