Horton

Re: Polyphase merge is obsolete

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-02-27T22:45:06Z
Lists: pgsql-hackers 
On Mon, Jan 16, 2017 at 5:56 PM, Peter Geoghegan <pg@heroku.com> wrote:
> On Wed, Oct 12, 2016 at 10:16 AM, Heikki Linnakangas <hlinnaka@iki.fi> wrote:
>> The number of *input* tapes we can use in each merge pass is still limited,
>> by the memory needed for the tape buffers and the merge heap, but only one
>> output tape is active at any time. The inactive output tapes consume very
>> few resources. So the whole idea of trying to efficiently reuse input tapes
>> as output tapes is pointless
>
> I picked this up again. The patch won't apply cleanly. Can you rebase?

Since we have an awful lot of stuff in the last CF, and this patch
doesn't seem particularly strategic, I've marked it "Returned with
Feedback".

Thanks
-- 
Peter Geoghegan

Commits

  1. Fix and clarify function comment on LogicalTapeSetCreate.

  2. Refactor LogicalTapeSet/LogicalTape interface.

  3. Replace polyphase merge algorithm with a simple balanced k-way merge.

  4. logtape.c: do not preallocate for tapes when sorting