diff options
| -rw-r--r-- | doc/src/sgml/ref/create_event_trigger.sgml | 11 | ||||
| -rw-r--r-- | src/backend/commands/event_trigger.c | 19 |
2 files changed, 28 insertions, 2 deletions
diff --git a/doc/src/sgml/ref/create_event_trigger.sgml b/doc/src/sgml/ref/create_event_trigger.sgml index 08894b22cfb..040df118153 100644 --- a/doc/src/sgml/ref/create_event_trigger.sgml +++ b/doc/src/sgml/ref/create_event_trigger.sgml @@ -108,7 +108,14 @@ CREATE EVENT TRIGGER <replaceable class="PARAMETER">name</replaceable> <title>Notes</title> <para> - To create a trigger on a event, the user must be superuser. + Only superusers can create event triggers. + </para> + + <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. </para> </refsect1> @@ -116,7 +123,7 @@ CREATE EVENT TRIGGER <replaceable class="PARAMETER">name</replaceable> <title>Examples</title> <para> - Forbid the execution of any <link linkend="ddl">ddl</link> command: + Forbid the execution of any <link linkend="ddl">DDL</link> command: <programlisting> CREATE OR REPLACE FUNCTION abort_any_command() diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c index cb4e658a584..1edffee410e 100644 --- a/src/backend/commands/event_trigger.c +++ b/src/backend/commands/event_trigger.c @@ -567,6 +567,25 @@ EventTriggerDDLCommandStart(Node *parsetree) EventTriggerData trigdata; /* + * Event Triggers are completely disabled in standalone mode. There are + * (at least) two reasons for this: + * + * 1. A sufficiently broken event trigger might not only render the + * database unusable, but prevent disabling itself to fix the situation. + * In this scenario, restarting in standalone mode provides an escape + * hatch. + * + * 2. BuildEventTriggerCache relies on systable_beginscan_ordered, and + * therefore will malfunction if pg_event_trigger's indexes are damaged. + * To allow recovery from a damaged index, we need some operating mode + * 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.) + */ + if (!IsUnderPostmaster) + return; + + /* * We want the list of command tags for which this procedure is actually * invoked to match up exactly with the list that CREATE EVENT TRIGGER * accepts. This debugging cross-check will throw an error if this |