database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-31 22:04:40 +03:00
Code Activity

Fix some issues in contrib/spi/refint.c.

Browse Source 
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
This commit is contained in:
Tom Lane
2025-04-07 15:54:09 -04:00
parent 8e293e689b
commit 8cfbdf8f4d
4 changed files with 55 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
doc/src/sgml/contrib-spi.sgml
View File

@ -36,7 +36,7 @@
<para>
<function>check_primary_key()</function> checks the referencing table.
To use, create a <literal>BEFORE INSERT OR UPDATE</literal> trigger using this
To use, create an <literal>AFTER INSERT OR UPDATE</literal> trigger using this
function on a table referencing another table. Specify as the trigger
arguments: the referencing table's column name(s) which form the foreign
key, the referenced table name, and the column names in the referenced table
@ -46,7 +46,7 @@
<para>
<function>check_foreign_key()</function> checks the referenced table.
To use, create a <literal>BEFORE DELETE OR UPDATE</literal> trigger using this
To use, create an <literal>AFTER DELETE OR UPDATE</literal> trigger using this
function on a table referenced by other table(s). Specify as the trigger
arguments: the number of referencing tables for which the function has to
perform checking, the action if a referencing key is found
@ -60,6 +60,16 @@
unique index.
</para>
<para>
Note that if these triggers are executed from
another <literal>BEFORE</literal> trigger, they can fail unexpectedly. For
example, if a user inserts row1 and then the <literal>BEFORE</literal>
trigger inserts row2 and calls a trigger with the
<function>check_foreign_key()</function>,
the <function>check_foreign_key()</function>
function will not see row1 and will fail.
</para>
<para>
There are examples in <filename>refint.example</filename>.
</para>