lockdefs.h

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/*-------------------------------------------------------------------------
 *
 * lockdefs.h
 *     Frontend exposed parts of postgres' low level lock mechanism
 *
 * The split between lockdefs.h and lock.h is not very principled. This file
 * contains definition that have to (indirectly) be available when included by
 * FRONTEND code.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/storage/lockdefs.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef LOCKDEFS_H_
#define LOCKDEFS_H_
 
/*
 * LOCKMODE is an integer (1..N) indicating a lock type.  LOCKMASK is a bit
 * mask indicating a set of held or requested lock types (the bit 1<<mode
 * corresponds to a particular lock mode).
 */
typedef int LOCKMASK;
typedef int LOCKMODE;
 
/*
 * These are the valid values of type LOCKMODE for all the standard lock
 * methods (both DEFAULT and USER).
 */
 
/* NoLock is not a lock mode, but a flag value meaning "don't get a lock" */
#define NoLock                  0
 
#define AccessShareLock         1   /* SELECT */
#define RowShareLock            2   /* SELECT FOR UPDATE/FOR SHARE */
#define RowExclusiveLock        3   /* INSERT, UPDATE, DELETE */
#define ShareUpdateExclusiveLock 4  /* VACUUM (non-FULL), ANALYZE, CREATE
                                     * INDEX CONCURRENTLY */
#define ShareLock               5   /* CREATE INDEX (WITHOUT CONCURRENTLY) */
#define ShareRowExclusiveLock   6   /* like EXCLUSIVE MODE, but allows ROW
                                     * SHARE */
#define ExclusiveLock           7   /* blocks ROW SHARE/SELECT...FOR UPDATE */
#define AccessExclusiveLock     8   /* ALTER TABLE, DROP TABLE, VACUUM FULL,
                                     * and unqualified LOCK TABLE */
 
#define MaxLockMode             8   /* highest standard lock mode */
 
/* See README.tuplock section "Locking to write inplace-updated tables" */
#define InplaceUpdateTupleLock ExclusiveLock
 
/* WAL representation of an AccessExclusiveLock on a table */
typedef struct xl_standby_lock
{
    TransactionId xid;          /* xid of holder of AccessExclusiveLock */
    Oid         dbOid;          /* DB containing table */
    Oid         relOid;         /* OID of table */
} xl_standby_lock;
 
#endif                          /* LOCKDEFS_H_ */