From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Alvaro Herrera <alvherre(at)atentus(dot)com> |
Cc: | Timur <itvthor(at)sdf(dot)lonestar(dot)org>, pgsql-general(at)postgresql(dot)org |
Subject: | Re: CREATE INDEX .. ON table1 (field1 asc, field2 desc) |
Date: | 2002-08-25 15:02:01 |
Message-ID: | 5805.1030287721@sss.pgh.pa.us |
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Lists: | pgsql-general |
Alvaro Herrera <alvherre(at)atentus(dot)com> writes:
>> I am new to PostgreSQL and databases in general, and I have this
>> question: why it is not possible to specify ordering when creating an
>> index?
> Because there is no point in doing so. Postgres automatically scans an
> index in reverse direction if you want to use descending order.
But he wants, or says he wants, ASC order on the first column and DESC
on the second. I concur with Martijn that this might just be a
beginner's mistake in giving the command ... but if that's really what
he wants then it doesn't correspond to either forward or reverse scan
of a normal index. You would indeed need to make a custom opclass for
the second column in order to make an index that can be scanned in this
order.
regards, tom lane
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