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Add GUC for temporarily disabling event triggers 

In order to troubleshoot misbehaving or buggy event triggers, the
documented advice is to enter single-user mode.  In an attempt to
reduce the number of situations where single-user mode is required
(or even recommended) for non-extraordinary maintenance, this GUC
allows to temporarily suspend event triggers.

This was originally extracted from a larger patchset which aimed
at supporting event triggers on login events.

Reviewed-by: Ted Yu <yuzhihong@gmail.com>
Reviewed-by: Mikhail Gribkov <youzhick@gmail.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Discussion: https://postgr.es/m/9140106E-F9BF-4D85-8FC8-F2D3C094A6D9@yesql.se
Discussion: https://postgr.es/m/0d46d29f-4558-3af9-9c85-7774e14a7709@postgrespro.ru
This commit is contained in:
Daniel Gustafsson 2023-09-25 12:41:49 +02:00
parent f19669fed3
commit 7750fefdb2
8 changed files with 98 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
doc/src/sgml/config.sgml
View File

@ -9425,6 +9425,25 @@ SET XML OPTION { DOCUMENT | CONTENT };
</listitem>
</varlistentry>
<varlistentry id="guc-event-triggers" xreflabel="event_triggers">
<term><varname>event_triggers</varname> (<type>boolean</type>)
<indexterm>
<primary><varname>event_triggers</varname></primary>
<secondary>configuration parameter</secondary>
</indexterm>
</term>
<listitem>
<para>
Allow temporarily disabling execution of event triggers in order to
troubleshoot and repair faulty event triggers. All event triggers will
be disabled by setting it to <literal>false</literal>. Setting the value
to <literal>true</literal> allows all event triggers to fire, this
is the default value. Only superusers and users with the appropriate
<literal>SET</literal> privilege can change this setting.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
<sect2 id="runtime-config-client-format">

9
doc/src/sgml/ref/create_event_trigger.sgml
View File

@ -121,9 +121,12 @@ CREATE EVENT TRIGGER <replaceable class="parameter">name</replaceable>
<para>
Event triggers are disabled in single-user mode (see <xref
linkend="app-postgres"/>). If an erroneous event trigger disables the
database so much that you can't even drop the trigger, restart in
single-user mode and you'll be able to do that.
linkend="app-postgres"/>) as well as when
<xref linkend="guc-event-triggers"/> is set to <literal>false</literal>.
If an erroneous event trigger disables the database so much that you can't
even drop the trigger, restart with <xref linkend="guc-event-triggers"/>
set to <literal>false</literal> to temporarily disable event triggers, or
in single-user mode, and you'll be able to do that.
</para>
</refsect1>

20
src/backend/commands/event_trigger.c
View File

@ -72,6 +72,9 @@ typedef struct EventTriggerQueryState
static EventTriggerQueryState *currentEventTriggerState = NULL;
/* GUC parameter */
bool event_triggers = true;
/* Support for dropped objects */
typedef struct SQLDropObject
{
@ -657,8 +660,11 @@ EventTriggerDDLCommandStart(Node *parsetree)
* wherein event triggers are disabled. (Or we could implement
* heapscan-and-sort logic for that case, but having disaster recovery
* scenarios depend on code that's otherwise untested isn't appetizing.)
*
* Additionally, event triggers can be disabled with a superuser-only GUC
* to make fixing database easier as per 1 above.
*/
if (!IsUnderPostmaster)
if (!IsUnderPostmaster || !event_triggers)
return;
runlist = EventTriggerCommonSetup(parsetree,
@ -692,9 +698,9 @@ EventTriggerDDLCommandEnd(Node *parsetree)
/*
* See EventTriggerDDLCommandStart for a discussion about why event
* triggers are disabled in single user mode.
* triggers are disabled in single user mode or via GUC.
*/
if (!IsUnderPostmaster)
if (!IsUnderPostmaster || !event_triggers)
return;
/*
@ -740,9 +746,9 @@ EventTriggerSQLDrop(Node *parsetree)
/*
* See EventTriggerDDLCommandStart for a discussion about why event
* triggers are disabled in single user mode.
* triggers are disabled in single user mode or via a GUC.
*/
if (!IsUnderPostmaster)
if (!IsUnderPostmaster || !event_triggers)
return;
/*
@ -811,9 +817,9 @@ EventTriggerTableRewrite(Node *parsetree, Oid tableOid, int reason)
/*
* See EventTriggerDDLCommandStart for a discussion about why event
* triggers are disabled in single user mode.
* triggers are disabled in single user mode or via a GUC.
*/
if (!IsUnderPostmaster)
if (!IsUnderPostmaster || !event_triggers)
return;
/*

11
src/backend/utils/misc/guc_tables.c
View File

@ -37,6 +37,7 @@
#include "catalog/namespace.h"
#include "catalog/storage.h"
#include "commands/async.h"
#include "commands/event_trigger.h"
#include "commands/tablespace.h"
#include "commands/trigger.h"
#include "commands/user.h"
@ -2000,6 +2001,16 @@ struct config_bool ConfigureNamesBool[] =
NULL, NULL, NULL
},
{
{"event_triggers", PGC_SUSET, CLIENT_CONN_STATEMENT,
gettext_noop("Enables event triggers."),
gettext_noop("When enabled, event triggers will fire for all applicable statements."),
},
&event_triggers,
true,
NULL, NULL, NULL
},
/* End-of-list marker */
{
{NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL, NULL

1
src/backend/utils/misc/postgresql.conf.sample
View File

@ -706,6 +706,7 @@
#xmloption = 'content'
#gin_pending_list_limit = 4MB
#createrole_self_grant = '' # set and/or inherit
#event_triggers = on
# - Locale and Formatting -

2
src/include/commands/event_trigger.h
View File

@ -29,6 +29,8 @@ typedef struct EventTriggerData
CommandTag tag;
} EventTriggerData;
extern PGDLLIMPORT bool event_triggers;
#define AT_REWRITE_ALTER_PERSISTENCE 0x01
#define AT_REWRITE_DEFAULT_VAL 0x02
#define AT_REWRITE_COLUMN_REWRITE 0x04

22
src/test/regress/expected/event_trigger.out
View File

@ -616,3 +616,25 @@ SELECT
DROP EVENT TRIGGER start_rls_command;
DROP EVENT TRIGGER end_rls_command;
DROP EVENT TRIGGER sql_drop_command;
-- Check the GUC for disabling event triggers
CREATE FUNCTION test_event_trigger_guc() RETURNS event_trigger
LANGUAGE plpgsql AS $$
DECLARE
obj record;
BEGIN
FOR obj IN SELECT * FROM pg_event_trigger_dropped_objects()
LOOP
RAISE NOTICE '% dropped %', tg_tag, obj.object_type;
END LOOP;
END;
$$;
CREATE EVENT TRIGGER test_event_trigger_guc
ON sql_drop
WHEN TAG IN ('DROP POLICY') EXECUTE FUNCTION test_event_trigger_guc();
SET event_triggers = 'on';
CREATE POLICY pguc ON event_trigger_test USING (FALSE);
DROP POLICY pguc ON event_trigger_test;
NOTICE: DROP POLICY dropped policy
CREATE POLICY pguc ON event_trigger_test USING (FALSE);
SET event_triggers = 'off';
DROP POLICY pguc ON event_trigger_test;

24
src/test/regress/sql/event_trigger.sql
View File

@ -471,3 +471,27 @@ SELECT
DROP EVENT TRIGGER start_rls_command;
DROP EVENT TRIGGER end_rls_command;
DROP EVENT TRIGGER sql_drop_command;
-- Check the GUC for disabling event triggers
CREATE FUNCTION test_event_trigger_guc() RETURNS event_trigger
LANGUAGE plpgsql AS $$
DECLARE
obj record;
BEGIN
FOR obj IN SELECT * FROM pg_event_trigger_dropped_objects()
LOOP
RAISE NOTICE '% dropped %', tg_tag, obj.object_type;
END LOOP;
END;
$$;
CREATE EVENT TRIGGER test_event_trigger_guc
ON sql_drop
WHEN TAG IN ('DROP POLICY') EXECUTE FUNCTION test_event_trigger_guc();
SET event_triggers = 'on';
CREATE POLICY pguc ON event_trigger_test USING (FALSE);
DROP POLICY pguc ON event_trigger_test;
CREATE POLICY pguc ON event_trigger_test USING (FALSE);
SET event_triggers = 'off';
DROP POLICY pguc ON event_trigger_test;