From: Tom Lane <tgl@sss.pgh.pa.us>
To: Steinar H. Gunderson <sgunderson@bigfoot.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Performance of ORDER BY
Date: Tue, 05 Dec 2006 13:39:16 -0500
Message-ID: <9446.1165343956@sss.pgh.pa.us> (raw)
In-Reply-To: <20061205181733.GA10309@uio.no>
References: <4575A863.6040504@varianinc.com>
<7090.1165341726@sss.pgh.pa.us>
<20061205181733.GA10309@uio.no>
"Steinar H. Gunderson" <sgunderson@bigfoot.com> writes:
> By the way, is the new sorting code any better for platforms that already
> have a decent qsort() (like Linux)?
It seemed better to us. Linux' qsort() is really mergesort, which is
better sometimes but often worse --- mergesort tends to have a less
CPU-cache-friendly memory access distribution. Another big problem with
the Linux version is that it pays no attention to sort_mem, but will
enthusiastically allocate lots of additional memory, thereby blowing
whatever cross-backend memory budgeting you might have been doing.
If you care there is quite a lot of discussion in the -hackers and
-performance archives from last spring or so.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, sgunderson@bigfoot.com
Subject: Re: Performance of ORDER BY
In-Reply-To: <9446.1165343956@sss.pgh.pa.us>
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