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For a long time, plpgsql has allowed trigger functions to parse references to OLD and NEW even if the current trigger event type didn't assign a value to one or the other variable; but actually executing such a reference would fail. The v11 changes to use "expanded records" for DTYPE_REC variables changed the behavior so that the unassigned variable now reads as a null composite value. While this behavioral change was more or less unintentional, it seems that leaving it like this is better than adding code and complexity to be bug-compatible with the old way. The change doesn't break any code that worked before, and it eliminates a gotcha that often required extra code to work around. Hence, update the docs to say that these variables are "null" not "unassigned" when not relevant to the event type. And add a regression test covering the behavior, so that we'll notice if we ever break it again. Per report from Kristjan Tammekivi. Discussion: https://postgr.es/m/CAABK7uL-uC9ZxKBXzo_68pKt7cECfNRv+c35CXZpjq6jCAzYYA@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: 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/.