Date: Tue, 3 May 2011 11:05:38 -0500
From: "Ross J. Reedstrom" <reedstrm@rice.edu>
To: pgsql-admin@postgresql.org
Subject: Re: simple question about using an empty string building
	a partial index
Message-ID: <20110503160537.GA434@rice.edu>
References: <BANLkTimkN8c4WVtNGQY0nbY_aPdR-yiEfg@mail.gmail.com>
	<4DBFA533.6080700@lelarge.info>
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On Tue, May 03, 2011 at 08:48:19AM +0200, Guillaume Lelarge wrote:
> On 05/03/2011 05:52 AM, Tom Hartnett wrote:
> > can it be done?
> > 
> > create index my_idx on my_table(col1) where col1='';
> > 
> > ERROR:  invalid input syntax for integer: ""
> > 
> > Seems simple enough but I don't know what the trick is.
> > 
> 
> col1 is an integer, not a string. And you cannot check for empty string
> in an integer column.
 
So if you've got a lot of records that display that column as an emtpy
string, it's actually probably filled with a NULL, so your index create
command would be something like:

create index my_idx on my_table(col1) where col1 is null;

Ross
-- 
Ross Reedstrom, Ph.D.                                 reedstrm@rice.edu
Systems Engineer & Admin, Research Scientist        phone: 713-348-6166
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Rice University MS-375, Houston, TX 77005
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