Horton

Re: Weird failure with latches in curculio on v15

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>, Tom Lane <tgl@sss.pgh.pa.us>, Thomas Munro <thomas.munro@gmail.com>, Fujii Masao <fujii@postgresql.org>, Postgres hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-02-06T00:07:50Z
Lists: pgsql-hackers 
Hi,

On 2023-02-05 15:57:47 -0800, Nathan Bossart wrote:
> > For the segment files, we'd likely need a parameter to indicate whether
> > the restore is random or not.
> 
> Wouldn't this approach still require each module to handle restoring ahead
> of time?

Yes, to some degree at least. I was just describing a few pretty obvious
improvements.

The core code can make that a lot easier though. The problem of where to
store such files can be provided by core code (presumably a separate
directory). A GUC for aggressiveness can be provided. Etc.


> I agree that the shell overhead isn't the main performance issue,
> but it's unclear to me how much of this should be baked into
> PostgreSQL.

I don't know fully either. But just reimplementing all of it in
different modules doesn't seem like a sane approach either. A lot of it
is policy that we need to solve once, centrally.


> I mean, we could introduce a GUC that tells us how far ahead to
> restore and have a background worker (or multiple background workers)
> asynchronously pull files into a staging directory via the callbacks.
> Is that the sort of scope you are envisioning?

Closer, at least.

Greetings,

Andres Freund

Commits

  1. Avoid calling proc_exit() in processes forked by system().

  2. Move extra code out of the Pre/PostRestoreCommand() section.

  3. Revert refactoring of restore command code to shell_restore.c

  4. Refactor code in charge of running shell-based recovery commands

  5. Clean up inconsistent use of fflush().

  6. Report wait events for local shell commands like archive_command.