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Commit5b148706c5exposed functionality that allows multiple processes to use the same replication origin, enabling non-builtin logical replication solutions to implement parallel apply for large transactions. With this functionality, if two backends acquire the same replication origin and one of them resets it first, the acquired_by flag is cleared without acknowledging that another backend is still actively using the origin. This can lead to the origin being unintentionally dropped. If the shared memory for that dropped origin is later reused for a newly created origin, the remaining backend that still holds a pointer to the old memory may inadvertently advance the LSN of a completely different origin, causing unpredictable behavior. Although the underlying issue predates commit5b148706c5, it did not surface earlier because the internal parallel apply worker mechanism correctly coordinated origin resets and drops. This commit resolves the problem by introducing a reference counter for replication origins. The reference count increases when a backend sets the origin and decreases when it resets it. Additionally, the backend that first acquires the origin will not release it until all other backends using the origin have released it as well. The patch also prevents dropping a replication origin when acquired_by is zero but the reference counter is nonzero, covering the scenario where the first session exits without properly releasing the origin. Author: Hou Zhijie <houzj.fnst@fujitsu.com> Author: Hayato Kuroda <kuroda.hayato@fujitsu.com> Reviewed-by: Shveta Malik <shveta.malik@gmail.com> Reviewed-by: Amit Kapila <amit.kapila16@gmail.com> Discussion: https://postgr.es/m/TY4PR01MB169077EE72ABE9E55BAF162D494B5A@TY4PR01MB16907.jpnprd01.prod.outlook.com Discussion: https://postgr.es/m/CAMPB6wfe4zLjJL8jiZV5kjjpwBM2=rTRme0UCL7Ra4L8MTVdOg@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.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.