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During an update of a PK row, we can skip firing the RI trigger if any old key value is NULL, because then the row could not have had any matching rows in the FK table. Conversely, during an update of an FK row, the outcome is determined if any new key value is NULL. In either case it becomes unnecessary to compare individual key values. This patch was inspired by discussion of Vik Reykja's patch to use IS NOT DISTINCT semantics for the key comparisons. In the event there is no need for that and so this patch looks nothing like his, but he should still get credit for having re-opened consideration of the trigger skip logic. |
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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. 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/.