From: "Anibal David Acosta" <aa@devshock.com>
To: "'Tom Lane'" <tgl@sss.pgh.pa.us>
Cc: <pgsql-performance@postgresql.org>
References: <004301cda8b4$fdc57bd0$f9507370$@devshock.com>
	<21823.1350074311@sss.pgh.pa.us>
In-Reply-To: <21823.1350074311@sss.pgh.pa.us>
Subject: Re: Do cast affects index usage?
Date: Fri, 12 Oct 2012 21:27:42 -0300
Message-ID: <000001cda8d9$913a7770$b3af6650$@devshock.com>
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Because I need to get all rows where datetime is greater than (for example)
'2012-10-10 00:00:00' but ignoring timezone, so basically I need to truncate
timezone
This can be done by converting to timestamp without timezone.


-----Mensaje original-----
De: Tom Lane [mailto:tgl@sss.pgh.pa.us] 
Enviado el: viernes, 12 de octubre de 2012 05:39 p.m.
Para: Anibal David Acosta
CC: pgsql-performance@postgresql.org
Asunto: Re: [PERFORM] Do cast affects index usage?

"Anibal David Acosta" <aa@devshock.com> writes:
> I have a table with a column of type timestamp with time zone, this 
> column has an index

> If I do a select like this
> select * from mytable where cast(my_date as timestamp without time 
> zone) >
> '2012-10-12 20:00:00'
> this query will use the index over the my_date column?

No.  The cast seems rather pointless though ...

			regards, tom lane