Horton

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

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Andres Freund <andres@anarazel.de>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Nathan Bossart <nathandbossart@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-02-15T01:26:41Z
Lists: pgsql-hackers 
On Tue, Feb 14, 2023 at 04:46:07PM -0800, Andres Freund wrote:
> Then it really shouldn't have been named pg_pwrite_zeros(). The point of the
> p{write,read}{,v} family of functions is to be able to specify the offset to
> read/write at. I assume the p is for position, but I'm not sure.

'p' could stand for POSIX, though both read() and pread() are in it.
Anyway, it looks that your guess may be right:
https://stackoverflow.com/questions/17877556/what-does-p-stand-for-in-function-names-pwrite-and-pread

Even there, people don't seem completely sure.
--
Michael

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.