From: Richard Neill <rn214@cam.ac.uk>
To: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: pgsql-bugs@postgresql.org
Subject: Re: BUG #5293: constant function (date_trunc) is repeatedly evaluated inside loop
Date: Wed, 20 Jan 2010 16:56:16 +0000
Message-ID: <4B5735B0.7050106@cam.ac.uk> (raw)
In-Reply-To: <4B56CA85020000250002E85A@gw.wicourts.gov>
References: <201001201423.o0KENXDR099157@wwwmaster.postgresql.org>
<4B56CA85020000250002E85A@gw.wicourts.gov>
Kevin Grittner wrote:
> "Richard Neill" <rn214@cam.ac.uk> wrote:
>
>> date_trunc('day', timestamp '2010-01-20 10:16:55')
>
> What happens with a "timestamp with time zone" literal?
>
> -Kevin
>
Good call!
This query is fast:
SELECT count(1) FROM tbl_tracker WHERE ((srep_timestamp >=
date_trunc('day', timestamp with time zone '2010-01-20 10:16:55') AND
srep_timestamp < date_trunc('day', timestamp with time zone '2010-01-20
10:16:55') + INTERVAL '24 hour' )) ;
In other words:
#fast
WHERE column < '2010-010-20 00:00:00'
#fast
WHERE column < date_trunc('day', timestamp with time zone
'2010-01-20 10:16:55')
#slow
WHERE column < date_trunc('day', timestamp
'2010-01-20 10:16:55')
Why is that, I wonder?
Richard
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To: pgsql-bugs@postgresql.org
Cc: rn214@cam.ac.uk, Kevin.Grittner@wicourts.gov
Subject: Re: BUG #5293: constant function (date_trunc) is repeatedly evaluated inside loop
In-Reply-To: <4B5735B0.7050106@cam.ac.uk>
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