Syntax support and documentation for event triggers.

They don't actually do anything yet; that will get fixed in a
follow-on commit.  But this gets the basic infrastructure in place,
including CREATE/ALTER/DROP EVENT TRIGGER; support for COMMENT,
SECURITY LABEL, and ALTER EXTENSION .. ADD/DROP EVENT TRIGGER;
pg_dump and psql support; and documentation for the anticipated
initial feature set.

Dimitri Fontaine, with review and a bunch of additional hacking by me.
Thom Brown extensively reviewed earlier versions of this patch set,
but there's not a whole lot of that code left in this commit, as it
turns out.

src/bin/psql/command.c

@@ -490,6 +490,9 @@ exec_command(const char *cmd,
 				else
 					success = listExtensions(pattern);
 				break;
+			case 'y':			/* Event Triggers */
+				success = listEventTriggers(pattern, show_verbose);
+				break;
 			default:
 				status = PSQL_CMD_UNKNOWN;
 		}

src/bin/psql/describe.c

@@ -2952,6 +2952,67 @@ listConversions(const char *pattern, bool verbose, bool showSystem)
 	return true;
 }
 
+/*
+ * \dy
+ *
+ * Describes Event Triggers.
+ */
+bool
+listEventTriggers(const char *pattern, bool verbose)
+{
+	PQExpBufferData buf;
+	PGresult   *res;
+	printQueryOpt myopt = pset.popt;
+	static const bool translate_columns[] =
+		{false, false, false, true, false, false, false};
+
+	initPQExpBuffer(&buf);
+
+	printfPQExpBuffer(&buf,
+					  "select evtname as \"%s\", "
+					  "evtevent as  \"%s\", "
+					  "pg_catalog.pg_get_userbyid(e.evtowner) AS \"%s\", "
+					  "case evtenabled when 'O' then 'enabled' "
+					  "  when 'R' then 'replica' "
+					  "  when 'A' then 'always' "
+					  "  when 'D' then 'disabled' end as  \"%s\", "
+					  "e.evtfoid::regproc as \"%s\", "
+					  "array_to_string(array(select x "
+					  "      from unnest(evttags) as t(x)), ', ') as  \"%s\" ",
+					  gettext_noop("Name"),
+					  gettext_noop("Event"),
+					  gettext_noop("Owner"),
+					  gettext_noop("Enabled"),
+					  gettext_noop("Procedure"),
+					  gettext_noop("Tags"));
+	if (verbose)
+		appendPQExpBuffer(&buf,
+						  ",\npg_catalog.obj_description(e.oid, 'pg_event_trigger') as \"%s\"",
+						  gettext_noop("Description"));
+	appendPQExpBuffer(&buf,
+					  "\nFROM pg_event_trigger e ");
+
+	processSQLNamePattern(pset.db, &buf, pattern, false, false,
+						  NULL, "evtname", NULL, NULL);
+
+	appendPQExpBuffer(&buf, "ORDER BY 1");
+
+	res = PSQLexec(buf.data, false);
+	termPQExpBuffer(&buf);
+	if (!res)
+		return false;
+
+	myopt.nullPrint = NULL;
+	myopt.title = _("List of event triggers");
+	myopt.translate_header = true;
+	myopt.translate_columns = translate_columns;
+
+	printQuery(res, &myopt, pset.queryFout, pset.logfile);
+
+	PQclear(res);
+	return true;
+}
+
 /*
  * \dC
  *

src/bin/psql/describe.h

@@ -96,4 +96,7 @@ extern bool listExtensions(const char *pattern);
 /* \dx+ */
 extern bool listExtensionContents(const char *pattern);
 
+/* \dy */
+extern bool listEventTriggers(const char *pattern, bool verbose);
+
 #endif   /* DESCRIBE_H */

src/bin/psql/help.c

@@ -229,6 +229,7 @@ slashUsage(unsigned short int pager)
 	fprintf(output, _("  \\dv[S+] [PATTERN]      list views\n"));
 	fprintf(output, _("  \\dE[S+] [PATTERN]      list foreign tables\n"));
 	fprintf(output, _("  \\dx[+]  [PATTERN]      list extensions\n"));
+	fprintf(output, _("  \\dy     [PATTERN]      list event triggers\n"));
 	fprintf(output, _("  \\l[+]                  list all databases\n"));
 	fprintf(output, _("  \\sf[+] FUNCNAME        show a function's definition\n"));
 	fprintf(output, _("  \\z      [PATTERN]      same as \\dp\n"));