Re: Problem with index in OR'd expression - Mailing list pgsql-general

From Ragnar
Subject Re: Problem with index in OR'd expression
Date
Msg-id 1167240470.6369.328.camel@localhost.localdomain
Whole thread Raw
In response to Re: Problem with index in OR'd expression  (postgresql.org@tgice.com)
Responses Re: Problem with index in OR'd expression
List pgsql-general
On mið, 2006-12-27 at 11:02 -0600, postgresql.org@tgice.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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