8e0c252753
When executing an UPDATE with a RETURNING clause on a table with a BEFORE UPDATE row trigger, the computation of the OLD values in the RETURNING list was incorrect if the target tuple was concurrently updated by another session, at isolation level READ COMMITTED. The problem was that the trigger code would lock the target tuple, waiting for the other session to commit, and then fetch the updated target tuple, but ExecUpdate() would not realise that the target tuple had changed, and use the outdated target tuple for computing OLD values. Fix by having ExecUpdate() check the TM_FailureData from trigger execution and re-fetch the target tuple if necessary. Re-fetching the target tuple like this is a little inefficient, but probably negligible compared to the trigger execution and update. A better long-term fix might be to move the EPQ code out of trigger.c, and let ExecUpdate() handle it, like ExecMergeMatched() does, but that would likely mean changing the trigger API, which seems a bit much for back-patching. Backpatch to v18, where support for RETURNING OLD/NEW was added. Bug: #19536 Reported-by: Jonas Boberg <bobergj@gmail.com> Diagnosed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> Author: Dean Rasheed <dean.a.rasheed@gmail.com> Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> Discussion: https://postgr.es/m/19536-73ce5847e6c0e7b1@postgresql.org Backpatch-through: 18 |
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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/.