Re: LP_DEAD hinting and not holding on to a buffer pin on leaf page(Was: [HACKERS] [WIP] Zipfian distribution in pgbench)

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От Peter Geoghegan
Тема Re: LP_DEAD hinting and not holding on to a buffer pin on leaf page(Was: [HACKERS] [WIP] Zipfian distribution in pgbench)
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Msg-id CAH2-Wz=pfZ3OM8X2jLQf3mJOJYUN2x04jL5SLEHd0YKMuyAt5g@mail.gmail.com
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Ответ на Re: LP_DEAD hinting and not holding on to a buffer pin on leaf page(Was: [HACKERS] [WIP] Zipfian distribution in pgbench)  (Peter Geoghegan <pg@bowt.ie>)
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On Fri, Aug 4, 2017 at 3:30 PM, Peter Geoghegan <pg@bowt.ie> wrote:
> Yura Sokolov of Postgres Pro performed this benchmark at my request.
> He took the 9.5 commit immediately proceeding 2ed5b87f9 as a baseline.

I attach a simple patch that comments out the release of the buffer
pin for logged tables where an MVCC snapshot is used for a scan that
is not an index-only scan. This is the simplest way of evaluating the
effects of disabling 2ed5b87f9. Yura or others may find this helpful.

To be clear, I am certainly not suggesting that we should revert
2ed5b87f9. I do think that we need to give serious thought to fixing
the regression that 2ed5b87f9 introduced for LP_DEAD setting by index
scans, though.

-- 
Peter Geoghegan

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