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Re: LIKE search and performance

From: James Mansion <james(at)mansionfamily(dot)plus(dot)com>
To: mark(at)mark(dot)mielke(dot)cc
Cc: Mark Lewis <mark(dot)lewis(at)mir3(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Alexander Staubo <alex(at)purefiction(dot)net>, Andy <frum(at)ar-sd(dot)net>, pgsql-performance(at)postgresql(dot)org
Subject: Re: LIKE search and performance
Date: 2007-06-06 22:23:13
Message-ID: 466733D1.1040308@mansionfamily.plus.com (view raw or flat)
Thread:
Lists: pgsql-performance
mark(at)mark(dot)mielke(dot)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.

James


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