Fix up foreign-key mechanism so that there is a sound semantic basis for the

equality checks it applies, instead of a random dependence on whatever
operators might be named "=".  The equality operators will now be selected
from the opfamily of the unique index that the FK constraint depends on to
enforce uniqueness of the referenced columns; therefore they are certain to be
consistent with that index's notion of equality.  Among other things this
should fix the problem noted awhile back that pg_dump may fail for foreign-key
constraints on user-defined types when the required operators aren't in the
search path.  This also means that the former warning condition about "foreign
key constraint will require costly sequential scans" is gone: if the
comparison condition isn't indexable then we'll reject the constraint
entirely. All per past discussions.

Along the way, make the RI triggers look into pg_constraint for their
information, instead of using pg_trigger.tgargs; and get rid of the always
error-prone fixed-size string buffers in ri_triggers.c in favor of building up
the RI queries in StringInfo buffers.

initdb forced due to columns added to pg_constraint and pg_trigger.

1 files changed, 31 insertions, 3 deletions

diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 8946cb73151..d6ff883c924 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.147 2007/01/30 01:33:36 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.148 2007/02/14 01:58:57 tgl Exp $
  *
  * NOTES
  *	  Eventually, the index information should go through here, too.
@@ -20,6 +20,7 @@
 #include "bootstrap/bootstrap.h"
 #include "catalog/pg_amop.h"
 #include "catalog/pg_amproc.h"
+#include "catalog/pg_constraint.h"
 #include "catalog/pg_namespace.h"
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
@@ -897,10 +898,37 @@ get_atttypetypmod(Oid relid, AttrNumber attnum,
 	ReleaseSysCache(tp);
 }
 
-/*				---------- INDEX CACHE ----------						 */
+/*				---------- CONSTRAINT CACHE ----------					 */
 
-/*		watch this space...
+/*
+ * get_constraint_name
+ *		Returns the name of a given pg_constraint entry.
+ *
+ * Returns a palloc'd copy of the string, or NULL if no such constraint.
+ *
+ * NOTE: since constraint name is not unique, be wary of code that uses this
+ * for anything except preparing error messages.
  */
+char *
+get_constraint_name(Oid conoid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache(CONSTROID,
+						ObjectIdGetDatum(conoid),
+						0, 0, 0);
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_constraint contup = (Form_pg_constraint) GETSTRUCT(tp);
+		char	   *result;
+
+		result = pstrdup(NameStr(contup->conname));
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return NULL;
+}
 
 /*				---------- OPCLASS CACHE ----------						 */