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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: Tomas Vondra <tomas.vondra@enterprisedb.com>, Tomas Vondra <tomas.vondra@2ndquadrant.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: 2020-11-25T03:57:47Z
Lists: pgsql-hackers 
On Thu, Nov 19, 2020 at 10:00 AM Stephen Frost <sfrost@snowman.net> wrote:
> * Thomas Munro (thomas.munro@gmail.com) wrote:
> > Hmm.  Every time I try to think of a protocol change for the
> > restore_command API that would be acceptable, I go around the same
> > circle of thoughts about event flow and realise that what we really
> > need for this is ... a WAL receiver...
>
> A WAL receiver, or an independent process which goes out ahead and
> fetches WAL..?

What I really meant was: why would you want this over streaming rep?
I just noticed this thread proposing to retire pg_standby on that
basis:

https://www.postgresql.org/message-id/flat/20201029024412.GP5380%40telsasoft.com

I'd be happy to see that land, to fix this problem with my plan.  But
are there other people writing restore scripts that block that would
expect them to work on PG14?

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