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107 lines
3.7 KiB
C
107 lines
3.7 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) 1996-2011, 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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* src/include/storage/relfilenode.h
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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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#include "storage/backendid.h"
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/*
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* The physical storage of a relation consists of one or more forks. The
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* main fork is always created, but in addition to that there can be
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* additional forks for storing various metadata. ForkNumber is used when
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* we need to refer to a specific fork in a relation.
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*/
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typedef enum ForkNumber
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{
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InvalidForkNumber = -1,
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MAIN_FORKNUM = 0,
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FSM_FORKNUM,
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VISIBILITYMAP_FORKNUM,
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INIT_FORKNUM
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/*
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* NOTE: if you add a new fork, change MAX_FORKNUM below and update the
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* forkNames array in catalog.c
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*/
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} ForkNumber;
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#define MAX_FORKNUM INIT_FORKNUM
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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, with the exception of the backend ID, which can be provided
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* separately. Note, however, that a "physical" relation is comprised of
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* multiple files on the filesystem, as each fork is stored as a separate
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* file, and each fork can be divided into multiple segments. See md.c.
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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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* Note: in pg_class, relfilenode can be zero to denote that the relation
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* is a "mapped" relation, whose current true filenode number is available
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* from relmapper.c. Again, this case is NOT allowed in RelFileNodes.
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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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* Augmenting a relfilenode with the backend ID provides all the information
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* we need to locate the physical storage.
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*/
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typedef struct RelFileNodeBackend
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{
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RelFileNode node;
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BackendId backend;
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} RelFileNodeBackend;
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/*
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* Note: RelFileNodeEquals and RelFileNodeBackendEquals compare relNode first
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* since that is most likely to be different in two unequal RelFileNodes. It
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* is probably redundant to compare spcNode if the other fields are found equal,
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* but do it 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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#define RelFileNodeBackendEquals(node1, node2) \
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((node1).node.relNode == (node2).node.relNode && \
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(node1).node.dbNode == (node2).node.dbNode && \
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(node1).backend == (node2).backend && \
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(node1).node.spcNode == (node2).node.spcNode)
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#endif /* RELFILENODE_H */
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