Re: Parallel tuplesort (for parallel B-Tree index creation)

From: Peter Geoghegan <pg(at)heroku(dot)com>
To: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Cc: Claudio Freire <klaussfreire(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Corey Huinker <corey(dot)huinker(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: Parallel tuplesort (for parallel B-Tree index creation)
Date: 2016-12-04 01:29:01
Message-ID: CAM3SWZQ0EgCxs2NoEUwB6BACi-pp5qVmp432i+Wh_XyUrg1FbQ@mail.gmail.com
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On Mon, Nov 7, 2016 at 8:28 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> What do we need to teach pg_restore about parallel CREATE INDEX, if
> anything at all? Could this be as simple as a blanket disabling of
> parallelism for CREATE INDEX from pg_restore? Or, does it need to be
> more sophisticated than that? I suppose that tools like reindexdb and
> pgbench must be considered in a similar way.

I still haven't resolved this question, which seems like the most
important outstanding question, but I attach V6. Changes:

* tuplesort.c was adapted to use the recently committed condition
variables stuff. This made things cleaner. No more ad-hoc WaitLatch()
looping.

* Adapted docs to mention the newly committed max_parallel_workers GUC
in the context of discussing proposed max_parallel_workers_maintenance
GUC.

* Fixed trivial assertion failure bug that could be tripped when a
conventional sort uses very little memory.

--
Peter Geoghegan

Attachment Content-Type Size
0002-Add-temporary-testing-tools.patch.gz application/x-gzip 4.7 KB
0001-Add-parallel-B-tree-index-build-sorting.patch.gz application/x-gzip 56.9 KB

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