From: Ibrahim Tekin <itekin@gmail.com>
To: mark@mark.mielke.cc <mark@mark.mielke.cc>
Cc: pgsql-performance@postgresql.org
Subject: Re: LIKE query on indexes
Date: Tue, 21 Feb 2006 22:12:17 +0200
Message-ID: <e4dcba670602211212i523ad54bh404bc1097f90ef6f@mail.gmail.com> (raw)
In-Reply-To: <20060221174048.GA8108@mark.mielke.cc>
References: <e4dcba670602210757n2caf7c15t2a93353c9081c51f@mail.gmail.com>
<20060221174048.GA8108@mark.mielke.cc>
my database encoding is unicode.
i have two table, one is 3.64gb on hdd and has 2.2 million records. it takes
140 secs to run on my AMD Turion 64 M 800MHz/1GB laptop.
second table is 1.2gb, 220000 records, and takes 56 secs to run.
explain says 'Seq Scan on mytable, ..'
On 2/21/06, mark@mark.mielke.cc <mark@mark.mielke.cc> wrote:
>
> On Tue, Feb 21, 2006 at 05:57:12PM +0200, Ibrahim Tekin wrote:
> > i have btree index on a text type field. i want see rows which starts
> with
> > certain characters on that field. so i write a query like this:
> > SELECT * FROM mytable WHERE myfield LIKE 'john%'
> > since this condition is from start of the field, query planner should
> use
> > index to find such elements but explain command shows me it will do a
> > sequential scan.
> > is this lack of a feature or i am wrong somewhere?
>
> Is the query fast enough? How big is your table? What does explain
> analyze select tell you?
>
> Cheers,
> mark
>
> --
> mark@mielke.cc / markm@ncf.ca / markm@nortel.com
> __________________________
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>
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To: pgsql-performance@postgresql.org
Cc: itekin@gmail.com, mark@mark.mielke.cc
Subject: Re: LIKE query on indexes
In-Reply-To: <e4dcba670602211212i523ad54bh404bc1097f90ef6f@mail.gmail.com>
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