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/*-------------------------------------------------------------------------
*
* relfilenode.h
* Physical access information for relations.
*
*
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/storage/relfilenode.h,v 1.25 2010/02/07 20:48:13 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef RELFILENODE_H
#define RELFILENODE_H
/*
* The physical storage of a relation consists of one or more forks. The
* main fork is always created, but in addition to that there can be
* additional forks for storing various metadata. ForkNumber is used when
* we need to refer to a specific fork in a relation.
*/
typedef enum ForkNumber
{
InvalidForkNumber = -1,
MAIN_FORKNUM = 0,
FSM_FORKNUM,
VISIBILITYMAP_FORKNUM
/*
* NOTE: if you add a new fork, change MAX_FORKNUM below and update the
* forkNames array in catalog.c
*/
} ForkNumber;
#define MAX_FORKNUM VISIBILITYMAP_FORKNUM
/*
* RelFileNode must provide all that we need to know to physically access
* a relation. Note, however, that a "physical" relation is comprised of
* multiple files on the filesystem, as each fork is stored as a separate
* file, and each fork can be divided into multiple segments. See md.c.
*
* 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.
*
* Note: in pg_class, relfilenode can be zero to denote that the relation
* is a "mapped" relation, whose current true filenode number is available
* from relmapper.c. Again, this case is NOT allowed in RelFileNodes.
*/
typedef struct RelFileNode
{
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).dbNode == (node2).dbNode && \
(node1).spcNode == (node2).spcNode)
#endif /* RELFILENODE_H */
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