Message-ID: <4A2FCD82.7000206@gmail.com>
Date: Wed, 10 Jun 2009 09:13:06 -0600
From: Rob Sargent <robjsargent@gmail.com>
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To: pgsql-sql@postgresql.org
References: <200906100519.34171.jfabiani@yolo.com>
	<347.1244643554@sss.pgh.pa.us>
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Subject: Re: setting the where clause


Tom Lane wrote:
> johnf <jfabiani@yolo.com> writes:
>   
>> I'm am programming in python using the Dabo modules.  www.dabodev.com if your 
>> interested.  Dabo is a framework that provides an easy way to build desktop 
>> app's.  To clear a data entry form. I have been setting the where clause 
>> to "where 1=0".  This of course retrieves 0 records and my form will display 
>> nothing.  It has been suggested that it might be better to set the where 
>> clause to a primary key value that does not exist in the table  "where PK 
>> = -9999999".   
>>     
>
> Whoever said that doesn't know what they're talking about.  It's not
> faster (because it forces an actual index probe to happen) and it's not
> safer (what if one day that PK value exists?).
>
> I'd personally go with "where false"; why not say what you mean rather
> than forcing humans and computers to deduce that the condition is
> constant false?
>
> 			regards, tom lane
>
>   

Of course you would do the world a favour if you wrote a client-side 
clear-the-screen routine that didn't pester the net and the server 
un-necessarily.