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

+        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