| From: | Bruno Wolff III <bruno(at)wolff(dot)to> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | John A Meinel <john(at)arbash-meinel(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, linux(at)alteeve(dot)com, tobias(at)nordicbet(dot)com, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Index ot being used |
| Date: | 2005-06-13 16:49:29 |
| Message-ID: | 20050613164929.GA12557@wolff.to |
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| Lists: | pgsql-performance |
On Mon, Jun 13, 2005 at 12:22:14 -0400,
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> I don't think the use-case has been shown that justifies doing this much
> work to ignore useless ORDER BY clauses. The examples that have come up
> in the past all suggest ignoring index columns not the other way 'round.
> Can you make a case that we need to do that part of it?
I don't think so. I don't think people are likely to order by constant
expressions except by adding them to the front to help optimization.
When I was thinking about this I was looking at what equivalences could
be used and didn't look back to see which ones would be useful in the
normal case. And I think it is a lot more likely people will leave out
columns they know not to be relevant than to include them.
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