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If a tuple was locked by transaction A, and transaction B updated it, the new version of the tuple created by B would be locked by A, yet visible only to B; due to an oversight in HeapTupleSatisfiesUpdate, the lock held by A wouldn't get checked if transaction B later deleted (or key-updated) the new version of the tuple. This might cause referential integrity checks to give false positives (that is, allow deletes that should have been rejected). This is an easy oversight to have made, because prior to improved tuple locks in commit 0ac5ad5134f it wasn't possible to have tuples created by our own transaction that were also locked by remote transactions, and so locks weren't even considered in that code path. It is recommended that foreign keys be rechecked manually in bulk after installing this update, in case some referenced rows are missing with some referencing row remaining. Per bug reported by Daniel Wood in CAPweHKe5QQ1747X2c0tA=5zf4YnS2xcvGf13Opd-1Mq24rF1cQ@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: http://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. Changes between all PostgreSQL releases are recorded in the file HISTORY. 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 http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.