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Re: Problem with index in OR'd expression

From: Ragnar <gnari(at)hive(dot)is>
To: postgresql(dot)org(at)tgice(dot)com
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Problem with index in OR'd expression
Date: 2006-12-27 17:27:50
Message-ID: 1167240470.6369.328.camel@localhost.localdomain (view raw or flat)
Thread:
Lists: pgsql-general
On miĆ°, 2006-12-27 at 11:02 -0600, postgresql(dot)org(at)tgice(dot)com wrote:
> 
> I was referring to the situation where one has this in a WHERE clause:
> 
>    ((vConstant IS NULL) OR (Table.IndexedCol = vConstant))
> 
> where vConstant is a *constant* parameter in a pl/pgsql function.

Reguardless of the issue whether pl/pgsql could be expected to
optimize this case, I find it difficult to imagine a scenario
where this kind of coding makes sense.

I understand that in some cases on would like to do this with
a *variable* to simplify logic, but what possible gain can
be had from doing this with a constant, other that obfuscation?

It does not make sense to spend CPU-time on  optimizing a case
that is not useful or common.

gnari



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Subject: Re: Problem with index in OR'd expression
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