Message-ID: <4C119B3E.3090608@squeakycode.net>
Date: Thu, 10 Jun 2010 21:11:10 -0500
From: Andy Colson <andy@squeakycode.net>
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To: David Jarvis <thangalin@gmail.com>, pgsql-performance@postgresql.org
Subject: Re: Analysis Function
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On 06/10/2010 07:41 PM, David Jarvis wrote:
> Hi,
>
> I found a slow part of the query:
>
> SELECT
> *  date(extract(YEAR FROM m.taken)||'-1-1') d1,*
> *  date(extract(YEAR FROM m.taken)||'-1-31') d2*
> FROM
>    climate.city c,
>    climate.station s,
>    climate.station_category sc,
>    climate.measurement m
> WHERE
> c.id <http://c.id> = 5148 AND ...
>
> Date extraction is 3.2 seconds, but without is 1.5 seconds. The PL/pgSQL
> code that actually runs (where p_month1, p_day1, and p_month2, p_day2
> are integers):
>
> *        date(extract(YEAR FROM
> m.taken)||''-'||p_month1||'-'||p_day1||''') d1,
>          date(extract(YEAR FROM
> m.taken)||''-'||p_month2||'-'||p_day2||''') d2
> *
> What is a better way to create those dates (without string
> concatenation, I presume)?
>
> Dave
>

I assume you are doing this in a loop?  Many Many Many times?  cuz:

andy=# select  date(extract(year from current_date) || '-1-1');
     date
------------
  2010-01-01
(1 row)

Time: 0.528 ms

Its pretty quick.  You say "without" its 1.5 seconds?  Thats all you change?  Can we see the sql and 'explain analyze' for both?

-Andy