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

Nathan Bossart <nathandbossart@gmail.com>

From: Nathan Bossart <nathandbossart@gmail.com>

To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>

Cc: Thomas Munro <thomas.munro@gmail.com>, Michael Paquier <michael@paquier.xyz>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>

Date: 2022-09-23T20:24:39Z

Lists: pgsql-hackers

+        PGAlignedXLogBlock zbuffer;
+
+        memset(zbuffer.data, 0, XLOG_BLCKSZ);

This seems excessive for only writing a single byte.

+#ifdef WIN32
+        /*
+         * XXX: It looks like on Windows, we need an explicit lseek() call here
+         * despite using pwrite() implementation from win32pwrite.c. Otherwise
+         * an error occurs.
+         */

I think this comment is too vague.  Can we describe the error in more
detail?  Or better yet, can we fix it as a prerequisite to this patch set?

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com

Commits

Revise pg_pwrite_zeros()
- ce340e530d1f 16.0 landed
Use pg_pwrite_zeros() in walmethods.c
- 28cc2976a9cf 16.0 landed
Introduce pg_pwrite_zeros() in fileutils.c
- 3bdbdf5d06f2 16.0 landed
Move pg_pwritev_with_retry() to src/common/file_utils.c
- 4ab8c81bd90a 16.0 landed
Restore pg_pread and friends.
- b6d8a60aba32 16.0 landed
Remove dead pread and pwrite replacement code.
- cf112c122060 16.0 cited