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Previously, the code and documentation seem to have essentially assumed than a call to pg_wal_replay_pause() would take place immediately, but that's not the case, because we only check for a pause in certain places. This means that a tool that uses this function and then wants to do something else afterward that is dependent on the pause having taken effect doesn't know how long it needs to wait to be sure that no more WAL is going to be replayed. To avoid that, add a new function pg_get_wal_replay_pause_state() which returns either 'not paused', 'paused requested', or 'paused'. After calling pg_wal_replay_pause() the status will immediate change from 'not paused' to 'pause requested'; when the startup process has noticed this, the status will change to 'pause'. For backward compatibility, pg_is_wal_replay_paused() still exists and returns the same thing as before: true if a pause has been requested, whether or not it has taken effect yet; and false if not. The documentation is updated to clarify. To improve the changes that a pause request is quickly confirmed effective, adjust things so that WaitForWALToBecomeAvailable will swiftly reach a call to recoveryPausesHere() when a pause request is made. Dilip Kumar, reviewed by Simon Riggs, Kyotaro Horiguchi, Yugo Nagata, Masahiko Sawada, and Bharath Rupireddy. Discussion: http://postgr.es/m/CAFiTN-vcLLWEm8Zr%3DYK83rgYrT9pbC8VJCfa1kY9vL3AUPfu6g%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/.