Horton

Re: Use pg_pwritev_with_retry() instead of write() in dir_open_for_write() to avoid partial writes?

Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>

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From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Nathan Bossart <nathandbossart@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-10-27T09:27:47Z
Lists: pgsql-hackers

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On Thu, Oct 27, 2022 at 11:24 AM Michael Paquier <michael@paquier.xyz> wrote:
>
> On Thu, Sep 29, 2022 at 08:09:56PM -0700, Nathan Bossart wrote:
> > Looks reasonable to me.
>
> 0001, to move pg_pwritev_with_retry() to a new home, seems fine, so
> applied.

Thanks.

> Regarding 0002, using pg_pwrite_zeros() as a routine name, as
> suggested by Thomas, sounds good to me.

Changed.

> However, I am not really a
> fan of its dependency with PGAlignedXLogBlock, because it should be
> able to work with any buffers of any sizes, as long as the input
> buffer is aligned, shouldn't it?  For example, what about
> PGAlignedBlock?  So, should we make this more extensible? My guess
> would be the addition of the block size and the block pointer to the
> arguments of pg_pwrite_zeros(), in combination with a check to make
> sure that the input buffer is MAXALIGN()'d (with an Assert() rather
> than just an elog/pg_log_error?).

+1 to pass in the aligned buffer, its size and an assertion on the buffer size.

Please see the attached v7 patch.

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

Commits

  1. Revise pg_pwrite_zeros()

  2. Use pg_pwrite_zeros() in walmethods.c

  3. Introduce pg_pwrite_zeros() in fileutils.c

  4. Move pg_pwritev_with_retry() to src/common/file_utils.c

  5. Restore pg_pread and friends.

  6. Remove dead pread and pwrite replacement code.