> -Original Message-
> From: Ron Peacetree [mailto:[EMAIL PROTECTED]
> Sent: Saturday, September 24, 2005 3:31 AM
> To: Dann Corbit; pgsql-hackers@postgresql.org; pgsql-
> [EMAIL PROTECTED]
> Subject: RE: [HACKERS] [PERFORM] Releasing memory during External
sortin
On Fri, 2005-09-23 at 12:48 -0400, Ron Peacetree wrote:
> > I have some indications from private tests that very high memory settings
> >may actually hinder performance of the sorts, though I cannot explain that
> >and wonder whether it is the performance tests themselves that have issues.
> >
> H
From: Dann Corbit <[EMAIL PROTECTED]>
Sent: Sep 23, 2005 5:38 PM
Subject: RE: [HACKERS] [PERFORM] Releasing memory during External sorting?
>_C Unleashed_ also explains how to use a callback function to perform
>arbitrary radix sorts (you simply need a method that returns the
>[b
t; [EMAIL PROTECTED] On Behalf Of Dann Corbit
> Sent: Friday, September 23, 2005 2:21 PM
> To: Ron Peacetree; Mark Lewis; Tom Lane; pgsql-hackers@postgresql.org;
> pgsql-performance@postgresql.org
> Subject: Re: [HACKERS] [PERFORM] Releasing memory during External
sorting?
>
> For
--Original Message-
> From: [EMAIL PROTECTED] [mailto:pgsql-hackers-
> [EMAIL PROTECTED] On Behalf Of Ron Peacetree
> Sent: Friday, September 23, 2005 11:41 AM
> To: Mark Lewis; Tom Lane; pgsql-hackers@postgresql.org; pgsql-
> [EMAIL PROTECTED]
> Subject: Re: [HACKERS] [PERFO
operations != passes. If you were clever, you could probably write a
modified bubble-sort algorithm that only made 2 passes. A pass is a
disk scan, operations are then performed (hopefully in memory) on what
you read from the disk. So there's no theoretical log N lower-bound on
the number of dis
Yep. Also, bear in mind that the lg(n!)= ~ nlgn - n lower bound on
the number of comparisions:
a= says nothing about the amount of data movement used.
b= only holds for generic comparison based sorting algorithms.
As Knuth says (vol 3, p180), Distribution Counting sorts without
ever comparing ele
From: Simon Riggs <[EMAIL PROTECTED]>
Sent: Sep 23, 2005 5:37 AM
Subject: [PERFORM] Releasing memory during External sorting?
>I have concerns about whether we are overallocating memory for use in
>external sorts. (All code relating to this is in tuplesort.c)
>
A decent external sorting algorithm,
From: Tom Lane <[EMAIL PROTECTED]>
Sent: Sep 23, 2005 2:15 PM
Subject: Re: [PERFORM] Releasing memory during External sorting?
>Mark Lewis <[EMAIL PROTECTED]> writes:
>> operations != passes. If you were clever, you could probably write a
>> modified bubble-sort algorithm that only made 2 passes
Mark Lewis <[EMAIL PROTECTED]> writes:
> operations != passes. If you were clever, you could probably write a
> modified bubble-sort algorithm that only made 2 passes. A pass is a
> disk scan, operations are then performed (hopefully in memory) on what
> you read from the disk. So there's no the
Ron Peacetree <[EMAIL PROTECTED]> writes:
> 2= No optimal external sorting algorithm should use more than 2 passes.
> 3= Optimal external sorting algorithms should use 1 pass if at all possible.
A comparison-based sort must use at least N log N operations, so it
would appear to me that if you have
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