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Re: WIP: WAL prefetch (another approach)

Thomas Munro <thomas.munro@gmail.com>

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From: Thomas Munro <thomas.munro@gmail.com>
To: Stephen Frost <sfrost@snowman.net>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Andres Freund <andres@anarazel.de>, David Steele <david@pgmasters.net>, Dmitry Dolgov <9erthalion6@gmail.com>, Jakub Wartak <Jakub.Wartak@tomtom.com>, Tom Lane <tgl@sss.pgh.pa.us>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Tomas Vondra <tomas.vondra@enterprisedb.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2021-05-10T04:11:08Z
Lists: pgsql-hackers 
On Thu, Apr 22, 2021 at 11:22 AM Stephen Frost <sfrost@snowman.net> wrote:
> On Wed, Apr 21, 2021 at 19:17 Thomas Munro <thomas.munro@gmail.com> wrote:
>> On Thu, Apr 22, 2021 at 8:16 AM Thomas Munro <thomas.munro@gmail.com> wrote:
>> ... Personally I think the right thing to do now is to revert it
>> and re-propose for 15 early in the cycle, supported with some better
>> testing infrastructure.
>
> I tend to agree with the idea to revert it, perhaps a +0 on that, but if others argue it should be fixed in-place, I wouldn’t complain about it.

Reverted.

Note: eelpout may return a couple of failures because it's set up to
run with recovery_prefetch=on (now an unknown GUC), and it'll be a few
hours before I can access that machine to adjust that...

> I very much encourage the idea of improving testing in this area and would be happy to try and help do so in the 15 cycle.

Cool.  I'm going to try out some ideas.

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix recovery_prefetch docs.

  2. Prefetch data referenced by the WAL, take II.

  3. Add circular WAL decoding buffer, take II.

  4. Fix generation of ./INSTALL for the distribution tarball

  5. Revert recovery prefetching feature.

  6. Sync guc.c and postgresql.conf.sample with the SGML docs.

  7. Add information of total data processed to replication slot stats.

  8. Doc: Review for "Optionally prefetch referenced data in recovery."

  9. Add circular WAL decoding buffer.

  10. Optionally prefetch referenced data in recovery.

  11. Remove read_page callback from XLogReader.

  12. Provide ReadRecentBuffer() to re-pin buffers by ID.

  13. Provide recovery_init_sync_method=syncfs.

  14. Mark factorial operator, and postfix operators in general, as deprecated.

  15. Rationalize GetWalRcv{Write,Flush}RecPtr().

  16. Support PrefetchBuffer() in recovery.

  17. Prevent hard failures of standbys caused by recycled WAL segments