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After processing the filemap to build the list of chunks that will be fetched from the source to rewing the target server, it is possible that a file which was previously processed is removed from the source. A simple example of such an occurence is a WAL segment which gets recycled on the target in-between. When the filemap is processed, files not categorized as relation files are first truncated to prepare for its full copy of which is going to be taken from the source, divided into a set of junks. However, for a recycled WAL segment, this would result in a segment which has a zero-byte size. With such an empty file, post-rewind recovery thinks that records are saved but they are actually not because of the truncation which happened when processing the filemap, resulting in data loss. In order to fix the problem, make sure that files which are found as removed on the source when receiving chunks of them are as well deleted on the target server for consistency. Back-patch to 9.5 where pg_rewind was added. Author: Tsunakawa Takayuki Reviewed-by: Michael Paquier Reported-by: Tsunakawa Takayuki Discussion: https://postgr.es/m/0A3221C70F24FB45833433255569204D1F8DAAA2%40G01JPEXMBYT05
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/.