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WAL_LOG does a scan of the template's pg_class to determine the set of relations that need to be copied from a template database to the new one. However, as coded in 9c08aea, this copy strategy would load the pages of pg_class without considering it as a permanent relation, causing the loaded pages to never be flushed when they should. Any modification of the template's pg_class, mostly through DDLs, would then be missed, causing corruptions. STRATEGY = WAL_LOG is the default over FILE_COPY since it has been introduced, so any changes done to pg_class on a database template would be gone. Updates of database templates should be a rare thing, so the impact of this bug should be hopefully limited. The pre-14 default strategy FILE_COPY is safe, and can be used as a workaround. Ryo Matsumura has found and analyzed the issue, and Nathan has written a test able to reproduce the failure (with few tweaks from me). Backpatch down to 15, where STRATEGY = WAL_LOG has been introduced. Author: Nathan Bossart, Ryo Matsumura Reviewed-by: Dilip Kumar, Michael Paquier Discussion: https://postgr.es/m/TYCPR01MB6868677E499C9AD5123084B5E8A39@TYCPR01MB6868.jpnprd01.prod.outlook.com Backpatch-through: 15
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/.