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Re: WIP: WAL prefetch (another approach)

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Stephen Frost <sfrost@snowman.net>, Alvaro Herrera <alvherre@2ndquadrant.com>, David Steele <david@pgmasters.net>, Dmitry Dolgov <9erthalion6@gmail.com>, Jakub Wartak <Jakub.Wartak@tomtom.com>, Tomas Vondra <tomas.vondra@enterprisedb.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2021-04-28T16:32:45Z
Lists: pgsql-hackers 
Hi,

On 2021-04-22 13:59:58 +1200, Thomas Munro wrote:
> On Thu, Apr 22, 2021 at 1:21 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > I've also tried to reproduce on 32-bit and 64-bit Intel, without
> > success.  So if this is real, maybe it's related to being big-endian
> > hardware?  But it's also quite sensitive to $dunno-what, maybe the
> > history of WAL records that have already been replayed.
> 
> Ah, that's interesting.  There are a couple of sparc64 failures and a
> ppc64 failure in the build farm, but I couldn't immediately spot what
> was wrong with them or whether it might be related to this stuff.
> 
> Thanks for the clues.  I'll see what unusual systems I can find to try
> this on....

FWIW, I've run 32 and 64 bit x86 through several hundred regression
cycles, without hitting an issue. For a lot of them I set
checkpoint_timeout to a lower value as I thought that might make it more
likely to reproduce an issue.

Tom, any chance you could check if your machine repros the issue before
these commits?

Greetings,

Andres Freund

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