Re: Performance of ORDER BY - Mailing list pgsql-performance

From Tom Lane
Subject Re: Performance of ORDER BY
Date
Msg-id 9446.1165343956@sss.pgh.pa.us
Whole thread Raw
In response to Re: Performance of ORDER BY  ("Steinar H. Gunderson" <sgunderson@bigfoot.com>)
List pgsql-performance
"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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