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61 lines
2.2 KiB
C
61 lines
2.2 KiB
C
/*-------------------------------------------------------------------------
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*
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* relfilenode.h
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* Physical access information for relations.
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*
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*
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* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/storage/relfilenode.h,v 1.15 2008/01/01 19:45:59 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef RELFILENODE_H
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#define RELFILENODE_H
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/*
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* RelFileNode must provide all that we need to know to physically access
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* a relation.
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*
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* spcNode identifies the tablespace of the relation. It corresponds to
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* pg_tablespace.oid.
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*
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* dbNode identifies the database of the relation. It is zero for
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* "shared" relations (those common to all databases of a cluster).
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* Nonzero dbNode values correspond to pg_database.oid.
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*
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* relNode identifies the specific relation. relNode corresponds to
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* pg_class.relfilenode (NOT pg_class.oid, because we need to be able
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* to assign new physical files to relations in some situations).
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* Notice that relNode is only unique within a particular database.
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*
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* Note: spcNode must be GLOBALTABLESPACE_OID if and only if dbNode is
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* zero. We support shared relations only in the "global" tablespace.
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*
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* Note: in pg_class we allow reltablespace == 0 to denote that the
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* relation is stored in its database's "default" tablespace (as
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* identified by pg_database.dattablespace). However this shorthand
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* is NOT allowed in RelFileNode structs --- the real tablespace ID
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* must be supplied when setting spcNode.
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*/
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typedef struct RelFileNode
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{
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Oid spcNode; /* tablespace */
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Oid dbNode; /* database */
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Oid relNode; /* relation */
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} RelFileNode;
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/*
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* Note: RelFileNodeEquals compares relNode first since that is most likely
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* to be different in two unequal RelFileNodes. It is probably redundant
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* to compare spcNode if the other two fields are found equal, but do it
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* anyway to be sure.
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*/
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#define RelFileNodeEquals(node1, node2) \
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((node1).relNode == (node2).relNode && \
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(node1).dbNode == (node2).dbNode && \
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(node1).spcNode == (node2).spcNode)
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#endif /* RELFILENODE_H */
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