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

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Use pg_pwritev_with_retry() instead of write() in dir_open_for_write() to avoid partial writes?
Date: 2022-08-06 06:41:18
Message-ID: Yu4NDi87SPpKiU/n@paquier.xyz
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On Fri, Aug 05, 2022 at 03:55:26PM +0530, Bharath Rupireddy wrote:
> I noticed that dir_open_for_write() in walmethods.c uses write() for
> WAL file initialization (note that this code is used by pg_receivewal
> and pg_basebackup) as opposed to core using pg_pwritev_with_retry() in
> XLogFileInitInternal() to avoid partial writes. Do we need to fix
> this?

0d56acfb has moved pg_pwritev_with_retry to be backend-only in fd.c :/

> Thoughts?

Makes sense to me for the WAL segment pre-padding initialization, as
we still want to point to the beginning of the segment after we are
done with the pre-padding, and the code has an extra lseek().
--
Michael

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