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Re: Bypassing useless ORDER BY in a VIEW


  • From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
  • To: "Robins Tharakan" <tharakan(at)gmail(dot)com>
  • Cc: pgsql-performance(at)postgresql(dot)org
  • Subject: Re: Bypassing useless ORDER BY in a VIEW
  • Date: Thu, 28 Feb 2008 12:13:40 -0500
  • Message-id: <8366.1204218820@sss.pgh.pa.us> <text/plain>

"Robins Tharakan" <tharakan(at)gmail(dot)com> writes:
> If I give an ORDER BY clause in a VIEW and then use it in another query
> where the VIEW's ORDER BY is immaterial, would the planner be able to
> discard this ORDER BY clause ?

No.  That's a feature not a bug; the sorts of cases where you want an
ORDER BY in a subquery, it's because you really want those rows computed
in that order (eg you've got side-effect-causing functions reading the
results).  Postgres will never discard an ORDER BY as "immaterial".

A rule of thumb is that ORDER BY in a view is bad design, IMHO.

			regards, tom lane



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