Date: Wed, 6 Jun 2007 23:33:52 -0400
From: mark@mark.mielke.cc
To: James Mansion <james@mansionfamily.plus.com>
Cc: Mark Lewis <mark.lewis@mir3.com>, Magnus Hagander <magnus@hagander.net>,
	Alexander Staubo <alex@purefiction.net>, Andy <frum@ar-sd.net>,
	pgsql-performance@postgresql.org
Subject: Re: LIKE search and performance
Message-ID: <20070607033352.GA2773@mark.mielke.cc>
References: <009501c79d4c$445428f0$0b00a8c0@mpsro.dom>
	<88daf38c0705230905u1a981102k691b47bd36011a80@mail.gmail.com>
	<4655DE75.4080506@mansionfamily.plus.com>
	<4655E64B.5050503@hagander.net>
	<4655FB8A.1040707@mansionfamily.plus.com>
	<1180040560.31471.262.camel@archimedes>
	<20070524215450.GA3858@mark.mielke.cc>
	<466733D1.1040308@mansionfamily.plus.com>
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On Wed, Jun 06, 2007 at 11:23:13PM +0100, James Mansion wrote:
> mark@mark.mielke.cc wrote:
> >What is a real life example where an intelligent and researched
> >database application would issue a like or ilike query as their
> >primary condition in a situation where they expected very high
> >selectivity?
> In my case the canonical example is to search against textual keys
> where the search is performed automatically if the user hs typed
> enough data and paused.  In almost all cases the '%' trails, and I'm
> looking for 'starts with' in effect.  usually the search will have a
> specified upper number of returned rows, if that's an available
> facility.  I realise in this case that matching against the index
> does not allow the match count unless we check MVCC as we go, but I
> don't see why another thread can't be doing that.

I believe PostgreSQL already considers using the index for "starts
with", so this wasn't part of the discussion for me. Sorry that this
wasn't clear.

Cheers,
mark

-- 
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