| From: | Michael Fuhr <mike(at)fuhr(dot)org> |
|---|---|
| To: | Karim Nassar <karim(dot)nassar(at)acm(dot)org> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Two queries are better than one? |
| Date: | 2005-07-29 01:53:22 |
| Message-ID: | 20050729015322.GA25003@winnie.fuhr.org |
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| Lists: | pgsql-performance |
On Thu, Jul 28, 2005 at 04:04:25PM -0700, Karim Nassar wrote:
> I ran into a situation today maintaining someone else's code where the
> sum time running 2 queries seems to be faster than 1. The original code
> was split into two queries. I thought about joining them, but
> considering the intelligence of my predecessor, I wanted to test it.
>
> The question is, which technique is really faster? Is there some hidden
> setup cost I don't see with explain analyze?
To see which technique will be faster in your application, time the
application code. The queries you show are taking fractions of a
millisecond; the communications overhead of executing two queries
might make that technique significantly slower than just the server
execution time that EXPLAIN ANALYZE shows.
--
Michael Fuhr
http://www.fuhr.org/~mfuhr/
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