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, 9 insertions, 1 deletions

diff --git a/src/include/rewrite/rewriteDefine.h b/src/include/rewrite/rewriteDefine.h
index d4673f82a6c..5b21cf8e797 100644
--- a/src/include/rewrite/rewriteDefine.h
+++ b/src/include/rewrite/rewriteDefine.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/rewrite/rewriteDefine.h,v 1.24 2007/03/13 00:33:43 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/rewrite/rewriteDefine.h,v 1.25 2007/03/19 23:38:32 wieck Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,6 +16,11 @@
 
 #include "nodes/parsenodes.h"
 
+#define	RULE_FIRES_ON_ORIGIN	'O'
+#define	RULE_FIRES_ALWAYS		'A'
+#define	RULE_FIRES_ON_REPLICA	'R'
+#define	RULE_DISABLED			'D'
+
 extern void DefineRule(RuleStmt *stmt, const char *queryString);
 
 extern void DefineQueryRewrite(char *rulename,
@@ -31,4 +36,7 @@ extern void RenameRewriteRule(Oid owningRel, const char *oldName,
 
 extern void setRuleCheckAsUser(Node *node, Oid userid);
 
+extern void EnableDisableRule(Relation rel, const char *rulename,
+				  char fires_when);
+
 #endif   /* REWRITEDEFINE_H */