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rescanLatestTimeLine() contains a guard against switching to a timeline that forked off from the current one prior to the current recovery point, but that guard does not work if the timeline switch occurs before the first WAL recod (which must be the checkpoint record) is read. Without this patch, an improper timeline switch is therefore possible in such cases. This happens because rescanLatestTimeLine() relies on the global variable EndRecPtr to understand the current position of WAL replay. However, EndRecPtr at this point in the code contains the endpoint of the last-replayed record, not the startpoint or endpoint of the record being replayed now. Thus, before any records have been replayed, it's zero, which causes the sanity check to always pass. To fix, pass down the correct timeline explicitly. The EndRecPtr value we want is the one from the xlogreader, which will be the starting position of the record we're about to try to read, rather than the global variable, which is the ending position of the last record we successfully read. They're usually the same, but not in the corner case described here. No back-patch, because in v14 and earlier branhes, we were using the wrong TLI here as well as the wrong LSN. In master, that was fixed by commit 4a92a1c3d1c361ffb031ed05bf65b801241d7cdd, but that and it's prerequisite patches are too invasive to back-patch for such a minor issue. Patch by me, reviewed by Amul Sul. Discussion: http://postgr.es/m/CA+Tgmoao96EuNeSPd+hspRKcsCddu=b1h-QNRuKfY8VmfNQdfg@mail.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/.