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

1 files changed, 98 insertions, 21 deletions

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index c08525c2e04..e2dadb7a7e2 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.213 2007/02/14 01:58:56 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.214 2007/03/19 23:38:29 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -54,6 +54,13 @@ static HeapTuple ExecCallTriggerFunc(TriggerData *trigdata,
 static void AfterTriggerSaveEvent(ResultRelInfo *relinfo, int event,
 					  bool row_trigger, HeapTuple oldtup, HeapTuple newtup);
 
+/*
+ * SessionReplicationRole -
+ *
+ *	Global variable that controls the trigger firing behaviour based
+ *	on pg_trigger.tgenabled. This is maintained from misc/guc.c.
+ */
+int	SessionReplicationRole = SESSION_REPLICATION_ROLE_ORIGIN;
 
 /*
  * Create a trigger.  Returns the OID of the created trigger.
@@ -270,7 +277,7 @@ CreateTrigger(CreateTrigStmt *stmt, Oid constraintOid)
 												  CStringGetDatum(trigname));
 	values[Anum_pg_trigger_tgfoid - 1] = ObjectIdGetDatum(funcoid);
 	values[Anum_pg_trigger_tgtype - 1] = Int16GetDatum(tgtype);
-	values[Anum_pg_trigger_tgenabled - 1] = BoolGetDatum(true);
+	values[Anum_pg_trigger_tgenabled - 1] = CharGetDatum(TRIGGER_FIRES_ON_ORIGIN);
 	values[Anum_pg_trigger_tgisconstraint - 1] = BoolGetDatum(stmt->isconstraint);
 	values[Anum_pg_trigger_tgconstrname - 1] = DirectFunctionCall1(namein,
 												CStringGetDatum(constrname));
@@ -701,11 +708,11 @@ renametrig(Oid relid,
  * EnableDisableTrigger()
  *
  *	Called by ALTER TABLE ENABLE/DISABLE TRIGGER
- *	to change 'tgenabled' flag for the specified trigger(s)
+ *	to change 'tgenabled' field for the specified trigger(s)
  *
  * rel: relation to process (caller must hold suitable lock on it)
  * tgname: trigger to process, or NULL to scan all triggers
- * enable: new value for tgenabled flag
+ * enable: new value for tgenabled field
  * skip_system: if true, skip "system" triggers (constraint triggers)
  *
  * Caller should have checked permissions for the table; here we also
@@ -714,7 +721,7 @@ renametrig(Oid relid,
  */
 void
 EnableDisableTrigger(Relation rel, const char *tgname,
-					 bool enable, bool skip_system)
+					 char fires_when, bool skip_system)
 {
 	Relation	tgrel;
 	int			nkeys;
@@ -765,13 +772,13 @@ EnableDisableTrigger(Relation rel, const char *tgname,
 
 		found = true;
 
-		if (oldtrig->tgenabled != enable)
+		if (oldtrig->tgenabled != fires_when)
 		{
 			/* need to change this one ... make a copy to scribble on */
 			HeapTuple	newtup = heap_copytuple(tuple);
 			Form_pg_trigger newtrig = (Form_pg_trigger) GETSTRUCT(newtup);
 
-			newtrig->tgenabled = enable;
+			newtrig->tgenabled = fires_when;
 
 			simple_heap_update(tgrel, &newtup->t_self, newtup);
 
@@ -1333,8 +1340,18 @@ ExecBSInsertTriggers(EState *estate, ResultRelInfo *relinfo)
 		Trigger    *trigger = &trigdesc->triggers[tgindx[i]];
 		HeapTuple	newtuple;
 
-		if (!trigger->tgenabled)
-			continue;
+		if (SessionReplicationRole == SESSION_REPLICATION_ROLE_REPLICA)
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_ORIGIN ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
+		else /* ORIGIN or LOCAL role */
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_REPLICA ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
 		LocTriggerData.tg_trigger = trigger;
 		newtuple = ExecCallTriggerFunc(&LocTriggerData,
 									   tgindx[i],
@@ -1382,8 +1399,18 @@ ExecBRInsertTriggers(EState *estate, ResultRelInfo *relinfo,
 	{
 		Trigger    *trigger = &trigdesc->triggers[tgindx[i]];
 
-		if (!trigger->tgenabled)
-			continue;
+		if (SessionReplicationRole == SESSION_REPLICATION_ROLE_REPLICA)
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_ORIGIN ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
+		else /* ORIGIN or LOCAL role */
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_REPLICA ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
 		LocTriggerData.tg_trigtuple = oldtuple = newtuple;
 		LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
 		LocTriggerData.tg_trigger = trigger;
@@ -1444,8 +1471,18 @@ ExecBSDeleteTriggers(EState *estate, ResultRelInfo *relinfo)
 		Trigger    *trigger = &trigdesc->triggers[tgindx[i]];
 		HeapTuple	newtuple;
 
-		if (!trigger->tgenabled)
-			continue;
+		if (SessionReplicationRole == SESSION_REPLICATION_ROLE_REPLICA)
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_ORIGIN ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
+		else /* ORIGIN or LOCAL role */
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_REPLICA ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
 		LocTriggerData.tg_trigger = trigger;
 		newtuple = ExecCallTriggerFunc(&LocTriggerData,
 									   tgindx[i],
@@ -1500,8 +1537,18 @@ ExecBRDeleteTriggers(EState *estate, ResultRelInfo *relinfo,
 	{
 		Trigger    *trigger = &trigdesc->triggers[tgindx[i]];
 
-		if (!trigger->tgenabled)
-			continue;
+		if (SessionReplicationRole == SESSION_REPLICATION_ROLE_REPLICA)
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_ORIGIN ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
+		else /* ORIGIN or LOCAL role */
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_REPLICA ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
 		LocTriggerData.tg_trigtuple = trigtuple;
 		LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
 		LocTriggerData.tg_trigger = trigger;
@@ -1575,8 +1622,18 @@ ExecBSUpdateTriggers(EState *estate, ResultRelInfo *relinfo)
 		Trigger    *trigger = &trigdesc->triggers[tgindx[i]];
 		HeapTuple	newtuple;
 
-		if (!trigger->tgenabled)
-			continue;
+		if (SessionReplicationRole == SESSION_REPLICATION_ROLE_REPLICA)
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_ORIGIN ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
+		else /* ORIGIN or LOCAL role */
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_REPLICA ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
 		LocTriggerData.tg_trigger = trigger;
 		newtuple = ExecCallTriggerFunc(&LocTriggerData,
 									   tgindx[i],
@@ -1636,8 +1693,18 @@ ExecBRUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
 	{
 		Trigger    *trigger = &trigdesc->triggers[tgindx[i]];
 
-		if (!trigger->tgenabled)
-			continue;
+		if (SessionReplicationRole == SESSION_REPLICATION_ROLE_REPLICA)
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_ORIGIN ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
+		else /* ORIGIN or LOCAL role */
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_REPLICA ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
 		LocTriggerData.tg_trigtuple = trigtuple;
 		LocTriggerData.tg_newtuple = oldtuple = newtuple;
 		LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
@@ -3267,8 +3334,18 @@ AfterTriggerSaveEvent(ResultRelInfo *relinfo, int event, bool row_trigger,
 		Trigger    *trigger = &trigdesc->triggers[tgindx[i]];
 
 		/* Ignore disabled triggers */
-		if (!trigger->tgenabled)
-			continue;
+		if (SessionReplicationRole == SESSION_REPLICATION_ROLE_REPLICA)
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_ORIGIN ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
+		else /* ORIGIN or LOCAL role */
+		{
+			if (trigger->tgenabled == TRIGGER_FIRES_ON_REPLICA ||
+				trigger->tgenabled == TRIGGER_DISABLED)
+				continue;
+		}
 
 		/*
 		 * If this is an UPDATE of a PK table or FK table that does not change