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8cfbdf8f4d
check_foreign_key incorrectly used a single cache entry for its saved plans for a 'c' (cascade) trigger, although there are two different queries to execute depending on whether it fires for an update or a delete. This caused the wrong things to be done if both types of event occur in one session. (This was indeed visible in the triggers regression test, but apparently nobody ever questioned it.) To fix, add the operation type to the cache key. Its debug log output failed to distinguish update from delete events, too. Also, change the intended trigger usage from BEFORE ROW to AFTER ROW, and add checks insisting on that usage. BEFORE is really rather unsafe, since if there are other BEFORE triggers they might change or cancel the operation we are trying to check. AFTER triggers are the standard way to propagate changes to other rows, so we should follow that way here. In passing, remove a useless duplicate lookup of the cache entry. This code is mostly intended as a documentation example, so we won't consider a back-patch. Author: Dmitrii Bondar <d.bondar@postgrespro.ru> Reviewed-by: Paul Jungwirth <pj@illuminatedcomputing.com> Reviewed-by: Lilian Ontowhee <ontowhee@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/79755a2b18ed4fe5e29da6a87a1e00d1@postgrespro.ru
The PostgreSQL contrib tree
---------------------------
This subtree contains porting tools, analysis utilities, and plug-in
features that are not part of the core PostgreSQL system, mainly
because they address a limited audience or are too experimental to be
part of the main source tree. This does not preclude their
usefulness.
User documentation for each module appears in the main SGML
documentation.
When building from the source distribution, these modules are not
built automatically, unless you build the "world" target. You can
also build and install them all by running "make all" and "make
install" in this directory; or to build and install just one selected
module, do the same in that module's subdirectory.
Some directories supply new user-defined functions, operators, or
types. To make use of one of these modules, after you have installed
the code you need to register the new SQL objects in the database
system by executing a CREATE EXTENSION command. In a fresh database,
you can simply do
CREATE EXTENSION module_name;
See the PostgreSQL documentation for more information about this
procedure.