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Re: WIP: WAL prefetch (another approach)

Stephen Frost <sfrost@snowman.net>

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From: Stephen Frost <sfrost@snowman.net>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Thomas Munro <thomas.munro@gmail.com>, Dmitry Dolgov <9erthalion6@gmail.com>, David Steele <david@pgmasters.net>, Andres Freund <andres@anarazel.de>, Alvaro Herrera <alvherre@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2020-06-06T00:36:32Z
Lists: pgsql-hackers 
Greetings,

* Tomas Vondra (tomas.vondra@2ndquadrant.com) wrote:
> I wonder if we can collect some stats to measure how effective the
> prefetching actually is. Ultimately we want something like cache hit
> ratio, but we're only preloading into page cache, so we can't easily
> measure that. Perhaps we could measure I/O timings in redo, though?

That would certainly be interesting, particularly as this optimization
seems likely to be useful on some platforms (eg, zfs, where the
filesystem block size is larger than ours..) and less on others
(traditional systems which have a smaller block size).

Thanks,

Stephen

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