Restructure operator classes to allow improved handling of cross-data-type

cases.  Operator classes now exist within "operator families".  While most
families are equivalent to a single class, related classes can be grouped
into one family to represent the fact that they are semantically compatible.
Cross-type operators are now naturally adjunct parts of a family, without
having to wedge them into a particular opclass as we had done originally.

This commit restructures the catalogs and cleans up enough of the fallout so
that everything still works at least as well as before, but most of the work
needed to actually improve the planner's behavior will come later.  Also,
there are not yet CREATE/DROP/ALTER OPERATOR FAMILY commands; the only way
to create a new family right now is to allow CREATE OPERATOR CLASS to make
one by default.  I owe some more documentation work, too.  But that can all
be done in smaller pieces once this infrastructure is in place.

src/backend/catalog/namespace.c

@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/namespace.c,v 1.88 2006/10/04 00:29:50 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/namespace.c,v 1.89 2006/12/23 00:43:09 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -27,6 +27,7 @@
 #include "catalog/pg_namespace.h"
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
+#include "catalog/pg_opfamily.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
 #include "commands/dbcommands.h"
@@ -1062,7 +1063,7 @@ OpclassIsVisible(Oid opcid)
 		 */
 		char	   *opcname = NameStr(opcform->opcname);
 
-		visible = (OpclassnameGetOpcid(opcform->opcamid, opcname) == opcid);
+		visible = (OpclassnameGetOpcid(opcform->opcmethod, opcname) == opcid);
 	}
 
 	ReleaseSysCache(opctup);
@@ -1070,6 +1071,89 @@ OpclassIsVisible(Oid opcid)
 	return visible;
 }
 
+/*
+ * OpfamilynameGetOpfid
+ *		Try to resolve an unqualified index opfamily name.
+ *		Returns OID if opfamily found in search path, else InvalidOid.
+ *
+ * This is essentially the same as TypenameGetTypid, but we have to have
+ * an extra argument for the index AM OID.
+ */
+Oid
+OpfamilynameGetOpfid(Oid amid, const char *opfname)
+{
+	Oid			opfid;
+	ListCell   *l;
+
+	recomputeNamespacePath();
+
+	foreach(l, namespaceSearchPath)
+	{
+		Oid			namespaceId = lfirst_oid(l);
+
+		opfid = GetSysCacheOid(OPFAMILYAMNAMENSP,
+							   ObjectIdGetDatum(amid),
+							   PointerGetDatum(opfname),
+							   ObjectIdGetDatum(namespaceId),
+							   0);
+		if (OidIsValid(opfid))
+			return opfid;
+	}
+
+	/* Not found in path */
+	return InvalidOid;
+}
+
+/*
+ * OpfamilyIsVisible
+ *		Determine whether an opfamily (identified by OID) is visible in the
+ *		current search path.  Visible means "would be found by searching
+ *		for the unqualified opfamily name".
+ */
+bool
+OpfamilyIsVisible(Oid opfid)
+{
+	HeapTuple	opftup;
+	Form_pg_opfamily opfform;
+	Oid			opfnamespace;
+	bool		visible;
+
+	opftup = SearchSysCache(OPFAMILYOID,
+							ObjectIdGetDatum(opfid),
+							0, 0, 0);
+	if (!HeapTupleIsValid(opftup))
+		elog(ERROR, "cache lookup failed for opfamily %u", opfid);
+	opfform = (Form_pg_opfamily) GETSTRUCT(opftup);
+
+	recomputeNamespacePath();
+
+	/*
+	 * Quick check: if it ain't in the path at all, it ain't visible. Items in
+	 * the system namespace are surely in the path and so we needn't even do
+	 * list_member_oid() for them.
+	 */
+	opfnamespace = opfform->opfnamespace;
+	if (opfnamespace != PG_CATALOG_NAMESPACE &&
+		!list_member_oid(namespaceSearchPath, opfnamespace))
+		visible = false;
+	else
+	{
+		/*
+		 * If it is in the path, it might still not be visible; it could be
+		 * hidden by another opfamily of the same name earlier in the path. So
+		 * we must do a slow check to see if this opfamily would be found by
+		 * OpfamilynameGetOpfid.
+		 */
+		char	   *opfname = NameStr(opfform->opfname);
+
+		visible = (OpfamilynameGetOpfid(opfform->opfmethod, opfname) == opfid);
+	}
+
+	ReleaseSysCache(opftup);
+
+	return visible;
+}
+
 /*
  * ConversionGetConid
  *		Try to resolve an unqualified conversion name.