5e6d561bc1
A cascading WAL sender doing logical decoding (as known as doing its work on a standby) has been using as flush LSN the value returned by GetStandbyFlushRecPtr() (last position safely flushed to disk). This is incorrect as such processes are only able to decode changes up to the LSN that has been replayed by the startup process. This commit changes cascading logical WAL senders to use the replay LSN, as returned by GetXLogReplayRecPtr(). This distinction is important particularly during shutdown, when WAL senders need to send any remaining available data to their clients, switching WAL senders to a caught-up state. Using the latest flush LSN rather than the replay LSN could cause the WAL senders to be stuck in an infinite loop preventing them to shut down, as the startup process does not run when WAL senders attempt to catch up, so they could keep waiting for work that would never happen. Backpatch down to v16, where logical decoding on standbys has been introduced. Author: Alexey Makhmutov <a.makhmutov@postgrespro.ru> Reviewed-by: Ajin Cherian <itsajin@gmail.com> Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com> Reviewed-by: Michael Paquier <michael@paquier.xyz> Discussion: https://postgr.es/m/52138028-7246-421c-9161-4fa108b88070@postgrespro.ru Backpatch-through: 16
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/.