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5c837f8fa0
The previous commit fixed some ways of losing an inplace update. It
remained possible to lose one when a backend working toward a
heap_update() copied a tuple into memory just before inplace update of
that tuple. In catalogs eligible for inplace update, use LOCKTAG_TUPLE
to govern admission to the steps of copying an old tuple, modifying it,
and issuing heap_update(). This includes MERGE commands. To avoid
changing most of the pg_class DDL, don't require LOCKTAG_TUPLE when
holding a relation lock sufficient to exclude inplace updaters.
Back-patch to v12 (all supported versions). In v13 and v12, "UPDATE
pg_class" or "UPDATE pg_database" can still lose an inplace update. The
v14+ UPDATE fix needs commit 86dc90056d,
and it wasn't worth reimplementing that fix without such infrastructure.
Reviewed by Nitin Motiani and (in earlier versions) Heikki Linnakangas.
Discussion: https://postgr.es/m/20231027214946.79.nmisch@google.com
62 lines
2.1 KiB
C
62 lines
2.1 KiB
C
/*-------------------------------------------------------------------------
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*
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* lockdefs.h
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* Frontend exposed parts of postgres' low level lock mechanism
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*
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* The split between lockdefs.h and lock.h is not very principled. This file
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* contains definition that have to (indirectly) be available when included by
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* FRONTEND code.
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*
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* Portions Copyright (c) 1996-2022, 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/lockdefs.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef LOCKDEFS_H_
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#define LOCKDEFS_H_
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/*
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* LOCKMODE is an integer (1..N) indicating a lock type. LOCKMASK is a bit
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* mask indicating a set of held or requested lock types (the bit 1<<mode
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* corresponds to a particular lock mode).
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*/
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typedef int LOCKMASK;
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typedef int LOCKMODE;
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/*
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* These are the valid values of type LOCKMODE for all the standard lock
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* methods (both DEFAULT and USER).
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*/
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/* NoLock is not a lock mode, but a flag value meaning "don't get a lock" */
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#define NoLock 0
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#define AccessShareLock 1 /* SELECT */
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#define RowShareLock 2 /* SELECT FOR UPDATE/FOR SHARE */
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#define RowExclusiveLock 3 /* INSERT, UPDATE, DELETE */
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#define ShareUpdateExclusiveLock 4 /* VACUUM (non-FULL),ANALYZE, CREATE INDEX
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* CONCURRENTLY */
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#define ShareLock 5 /* CREATE INDEX (WITHOUT CONCURRENTLY) */
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#define ShareRowExclusiveLock 6 /* like EXCLUSIVE MODE, but allows ROW
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* SHARE */
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#define ExclusiveLock 7 /* blocks ROW SHARE/SELECT...FOR UPDATE */
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#define AccessExclusiveLock 8 /* ALTER TABLE, DROP TABLE, VACUUM FULL,
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* and unqualified LOCK TABLE */
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#define MaxLockMode 8 /* highest standard lock mode */
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/* See README.tuplock section "Locking to write inplace-updated tables" */
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#define InplaceUpdateTupleLock ExclusiveLock
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/* WAL representation of an AccessExclusiveLock on a table */
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typedef struct xl_standby_lock
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{
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TransactionId xid; /* xid of holder of AccessExclusiveLock */
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Oid dbOid; /* DB containing table */
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Oid relOid; /* OID of table */
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} xl_standby_lock;
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#endif /* LOCKDEFS_H_ */
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