Changes pg_trigger and extend pg_rewrite in order to allow triggers and

rules to be defined with different, per session controllable, behaviors
for replication purposes.

This will allow replication systems like Slony-I and, as has been stated
on pgsql-hackers, other products to control the firing mechanism of
triggers and rewrite rules without modifying the system catalog directly.

The firing mechanisms are controlled by a new superuser-only GUC
variable, session_replication_role, together with a change to
pg_trigger.tgenabled and a new column pg_rewrite.ev_enabled. Both
columns are a single char data type now (tgenabled was a bool before).
The possible values in these attributes are:

     'O' - Trigger/Rule fires when session_replication_role is "origin"
           (default) or "local". This is the default behavior.

     'D' - Trigger/Rule is disabled and fires never

     'A' - Trigger/Rule fires always regardless of the setting of
           session_replication_role

     'R' - Trigger/Rule fires when session_replication_role is "replica"

The GUC variable can only be changed as long as the system does not have
any cached query plans. This will prevent changing the session role and
accidentally executing stored procedures or functions that have plans
cached that expand to the wrong query set due to differences in the rule
firing semantics.

The SQL syntax for changing a triggers/rules firing semantics is

     ALTER TABLE <tabname> <when> TRIGGER|RULE <name>;

     <when> ::= ENABLE | ENABLE ALWAYS | ENABLE REPLICA | DISABLE

psql's \d command as well as pg_dump are extended in a backward
compatible fashion.

Jan

src/bin/pg_dump/pg_dump.c

@@ -12,7 +12,7 @@
  *	by PostgreSQL
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/bin/pg_dump/pg_dump.c,v 1.460 2007/02/14 01:58:57 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/bin/pg_dump/pg_dump.c,v 1.461 2007/03/19 23:38:30 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3699,15 +3699,26 @@ getRules(int *numRules)
 	int			i_ruletable;
 	int			i_ev_type;
 	int			i_is_instead;
+	int			i_ev_enabled;
 
 	/* Make sure we are in proper schema */
 	selectSourceSchema("pg_catalog");
 
-	if (g_fout->remoteVersion >= 70100)
+	if (g_fout->remoteVersion >= 80300)
 	{
 		appendPQExpBuffer(query, "SELECT "
 						  "tableoid, oid, rulename, "
-						  "ev_class as ruletable, ev_type, is_instead "
+						  "ev_class as ruletable, ev_type, is_instead, "
+						  "ev_enabled "
+						  "FROM pg_rewrite "
+						  "ORDER BY oid");
+	}
+	else if (g_fout->remoteVersion >= 70100)
+	{
+		appendPQExpBuffer(query, "SELECT "
+						  "tableoid, oid, rulename, "
+						  "ev_class as ruletable, ev_type, is_instead, "
+						  "'O'::char as ev_enabled "
 						  "FROM pg_rewrite "
 						  "ORDER BY oid");
 	}
@@ -3716,7 +3727,8 @@ getRules(int *numRules)
 		appendPQExpBuffer(query, "SELECT "
 						  "(SELECT oid FROM pg_class WHERE relname = 'pg_rewrite') AS tableoid, "
 						  "oid, rulename, "
-						  "ev_class as ruletable, ev_type, is_instead "
+						  "ev_class as ruletable, ev_type, is_instead, "
+						  "'O'::char as ev_enabled "
 						  "FROM pg_rewrite "
 						  "ORDER BY oid");
 	}
@@ -3736,6 +3748,7 @@ getRules(int *numRules)
 	i_ruletable = PQfnumber(res, "ruletable");
 	i_ev_type = PQfnumber(res, "ev_type");
 	i_is_instead = PQfnumber(res, "is_instead");
+	i_ev_enabled = PQfnumber(res, "ev_enabled");
 
 	for (i = 0; i < ntups; i++)
 	{
@@ -3759,6 +3772,7 @@ getRules(int *numRules)
 		ruleinfo[i].dobj.dump = ruleinfo[i].ruletable->dobj.dump;
 		ruleinfo[i].ev_type = *(PQgetvalue(res, i, i_ev_type));
 		ruleinfo[i].is_instead = *(PQgetvalue(res, i, i_is_instead)) == 't';
+		ruleinfo[i].ev_enabled = *(PQgetvalue(res, i, i_ev_enabled));
 		if (ruleinfo[i].ruletable)
 		{
 			/*
@@ -3956,7 +3970,7 @@ getTriggers(TableInfo tblinfo[], int numTables)
 			tginfo[j].tgnargs = atoi(PQgetvalue(res, j, i_tgnargs));
 			tginfo[j].tgargs = strdup(PQgetvalue(res, j, i_tgargs));
 			tginfo[j].tgisconstraint = *(PQgetvalue(res, j, i_tgisconstraint)) == 't';
-			tginfo[j].tgenabled = *(PQgetvalue(res, j, i_tgenabled)) == 't';
+			tginfo[j].tgenabled = *(PQgetvalue(res, j, i_tgenabled));
 			tginfo[j].tgdeferrable = *(PQgetvalue(res, j, i_tgdeferrable)) == 't';
 			tginfo[j].tginitdeferred = *(PQgetvalue(res, j, i_tginitdeferred)) == 't';
 
@@ -8824,11 +8838,27 @@ dumpTrigger(Archive *fout, TriggerInfo *tginfo)
 	}
 	appendPQExpBuffer(query, ");\n");
 
-	if (!tginfo->tgenabled)
+	if (tginfo->tgenabled != 't' && tginfo->tgenabled != 'O')
 	{
 		appendPQExpBuffer(query, "\nALTER TABLE %s ",
 						  fmtId(tbinfo->dobj.name));
-		appendPQExpBuffer(query, "DISABLE TRIGGER %s;\n",
+		switch (tginfo->tgenabled)
+		{
+			case 'D':
+			case 'f':
+				appendPQExpBuffer(query, "DISABLE");
+				break;
+			case 'A':
+				appendPQExpBuffer(query, "ENABLE ALWAYS");
+				break;
+			case 'R':
+				appendPQExpBuffer(query, "ENABLE REPLICA");
+				break;
+			default:
+				appendPQExpBuffer(query, "ENABLE");
+				break;
+		}
+		appendPQExpBuffer(query, " TRIGGER %s;\n",
 						  fmtId(tginfo->dobj.name));
 	}
 
@@ -8914,6 +8944,33 @@ dumpRule(Archive *fout, RuleInfo *rinfo)
 
 	printfPQExpBuffer(cmd, "%s\n", PQgetvalue(res, 0, 0));
 
+	/*
+	 * Add the command to alter the rules replication firing semantics
+	 * if it differs from the default.
+	 */
+	if (rinfo->ev_enabled != 'O')
+	{
+		appendPQExpBuffer(cmd, "ALTER TABLE %s.",
+					fmtId(tbinfo->dobj.namespace->dobj.name));
+		appendPQExpBuffer(cmd, "%s ",
+					fmtId(tbinfo->dobj.name));
+		switch (rinfo->ev_enabled)
+		{
+			case 'A':
+				appendPQExpBuffer(cmd, "ENABLE ALWAYS RULE %s;\n",
+							fmtId(rinfo->dobj.name));
+				break;
+			case 'R':
+				appendPQExpBuffer(cmd, "ENABLE REPLICA RULE %s;\n",
+							fmtId(rinfo->dobj.name));
+				break;
+			case 'D':
+				appendPQExpBuffer(cmd, "DISABLE RULE %s;\n",
+							fmtId(rinfo->dobj.name));
+				break;
+		}
+	}
+
 	/*
 	 * DROP must be fully qualified in case same name appears in pg_catalog
 	 */