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This routine is designed to write zeros to a file using vectored I/O, for a size given by its caller, being useful when it comes to initializing a file with a final size already known. XLogFileInitInternal() in xlog.c is changed to use this new routine when initializing WAL segments with zeros (wal_init_zero enabled). Note that the aligned buffers used for the vectored I/O writes have a size of XLOG_BLCKSZ, and not BLCKSZ anymore, as pg_pwrite_zeros() relies on PGAlignedBlock while xlog.c originally used PGAlignedXLogBlock. This routine will be used in a follow-up patch to do the pre-padding of WAL segments for pg_receivewal and pg_basebackup when these are not compressed. Author: Bharath Rupireddy Reviewed-by: Nathan Bossart, Andres Freund, Thomas Munro, Michael Paquier Discussion: https://www.postgresql.org/message-id/CALj2ACUq7nAb7%3DbJNbK3yYmp-SZhJcXFR_pLk8un6XgDzDF3OA%40mail.gmail.com
PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download/ See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.