Tablespaces. Alternate database locations are dead, long live tablespaces.

There are various things left to do: contrib dbsize and oid2name modules
need work, and so does the documentation.  Also someone should think about
COMMENT ON TABLESPACE and maybe RENAME TABLESPACE.  Also initlocation is
dead, it just doesn't know it yet.

Gavin Sherry and Tom Lane.

1 files changed, 47 insertions, 9 deletions

diff --git a/src/include/storage/relfilenode.h b/src/include/storage/relfilenode.h
index 715dc00f7de..d430412e67f 100644
--- a/src/include/storage/relfilenode.h
+++ b/src/include/storage/relfilenode.h
@@ -1,22 +1,60 @@
+/*-------------------------------------------------------------------------
+ *
+ * relfilenode.h
+ *	  Physical access information for relations.
+ *
+ *
+ * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * $PostgreSQL: pgsql/src/include/storage/relfilenode.h,v 1.9 2004/06/18 06:14:13 tgl Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
 #ifndef RELFILENODE_H
 #define RELFILENODE_H
 
 /*
- * This is all what we need to know to find relation file.
- * tblNode is identificator of tablespace and because of
- * currently our tablespaces are equal to databases this is
- * database OID. relNode is currently relation OID on creation
- * but may be changed later if required. relNode is stored in
- * pg_class.relfilenode.
+ * RelFileNode must provide all that we need to know to physically access
+ * a relation.
+ *
+ * spcNode identifies the tablespace of the relation.  It corresponds to
+ * pg_tablespace.oid.
+ *
+ * dbNode identifies the database of the relation.  It is zero for
+ * "shared" relations (those common to all databases of a cluster).
+ * Nonzero dbNode values correspond to pg_database.oid.
+ *
+ * relNode identifies the specific relation.  relNode corresponds to
+ * pg_class.relfilenode (NOT pg_class.oid, because we need to be able
+ * to assign new physical files to relations in some situations).
+ * Notice that relNode is only unique within a particular database.
+ *
+ * Note: spcNode must be GLOBALTABLESPACE_OID if and only if dbNode is
+ * zero.  We support shared relations only in the "global" tablespace.
+ *
+ * Note: in pg_class we allow reltablespace == 0 to denote that the
+ * relation is stored in its database's "default" tablespace (as
+ * identified by pg_database.dattablespace).  However this shorthand
+ * is NOT allowed in RelFileNode structs --- the real tablespace ID
+ * must be supplied when setting spcNode.
  */
 typedef struct RelFileNode
 {
-	Oid			tblNode;		/* tablespace */
+	Oid			spcNode;		/* tablespace */
+	Oid			dbNode;			/* database */
 	Oid			relNode;		/* relation */
 } RelFileNode;
 
+/*
+ * Note: RelFileNodeEquals compares relNode first since that is most likely
+ * to be different in two unequal RelFileNodes.  It is probably redundant
+ * to compare spcNode if the other two fields are found equal, but do it
+ * anyway to be sure.
+ */
 #define RelFileNodeEquals(node1, node2) \
 	((node1).relNode == (node2).relNode && \
-	 (node1).tblNode == (node2).tblNode)
+	 (node1).dbNode == (node2).dbNode && \
+	 (node1).spcNode == (node2).spcNode)
 
-#endif   /* RELFILENODE_H */
+#endif /* RELFILENODE_H */