6ede13d1b5
When executing a MERGE UPDATE action, if there is more than one concurrent update of the target row, the lock-and-retry code would sometimes incorrectly identify the latest version of the target tuple, leading to incorrect results. This was caused by using the ctid field from the TM_FailureData returned by table_tuple_lock() in a case where the result was TM_Ok, which is unsafe because the TM_FailureData struct is not guaranteed to be fully populated in that case. Instead, it should use the tupleid passed to (and updated by) table_tuple_lock(). To reduce the chances of similar errors in the future, improve the commentary for table_tuple_lock() and TM_FailureData to make it clearer that table_tuple_lock() updates the tid passed to it, and most fields of TM_FailureData should not be relied on in non-failure cases. An exception to this is the "traversed" field, which is set in both success and failure cases. Reported-by: Dmitry <dsy.075@yandex.ru> Author: Yugo Nagata <nagata@sraoss.co.jp> Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com> Reviewed-by: Chao Li <li.evan.chao@gmail.com> Discussion: https://postgr.es/m/1570d30e-2b95-4239-b9c3-f7bf2f2f8556@yandex.ru 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.
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/.