Re: +Sort hint

From: Nuno Souto <nsouto_at_nsw.bigpond.net.au>
Date: Tue, 6 Jul 1999 23:06:52 +1000
Message-ID: <7lt0bt$mep$4@m2.c2.telstra-mm.net.au>

Pre-sorting can be interesting to performance.

Say you have a column(s) that has a non-unique index on it.

If you pre-sort on the column(s), all the rows of that same index key value will most likely be in the same block. One single read operation gets them all. As opposed to storing the rows in any other order and trying to retrieve by this same index, which can cause "hidden" multiple reads.

Kind of a poor-man's clustering, really.

You can do the same with ORACLE clustering on a single table, instead of the "textbook" clustering of two tables.

--
Cheers
Nuno Souto
nsouto_at_nsw.bigpond.net.au.nospam
Is there a nospam domain?
http://www.users.bigpond.net.au/the_Den Doug Cowles <dcowles_at_bigfoot.com> wrote in message news:37814D8C.D6BF65EF_at_bigfoot.com...
> I was using an automated tuning tool that recommended I place the data
> into the
> table in sorted order, and then user a +Sort hint to expedite a query.
>
> I thought that Oracle pretty much returned the data any way it felt like
> it regardless
> of when I put it in. What good will pre-sorting data do?
>
Received on Tue Jul 06 1999 - 08:06:52 CDT