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.
Hmmm.
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
[bucketsize] most
I have concerns about whether we are overallocating memory for use in
external sorts. (All code relating to this is in tuplesort.c)
When we begin a sort we allocate (work_mem | maintenance_work_mem) and
attempt to do the sort in memory. If the sort set is too big to fit in
memory we then write to
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 haven't
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
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
Message-
From: Mark Lewis [EMAIL PROTECTED]
Sent: Sep 23, 2005 1:43 PM
To: Tom Lane [EMAIL PROTECTED]
Subject: Re: [PERFORM] Releasing memory during External sorting?
operations != passes. If you were clever, you could probably write a
modified bubble-sort algorithm that only made 2 passes
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
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, say
