lockoptions.h

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/*-------------------------------------------------------------------------
 *
 * lockoptions.h
 *    Common header for some locking-related declarations.
 *
 *
 * Copyright (c) 2014-2026, PostgreSQL Global Development Group
 *
 * src/include/nodes/lockoptions.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef LOCKOPTIONS_H
#define LOCKOPTIONS_H
 
/*
 * This enum represents the different strengths of FOR UPDATE/SHARE clauses.
 * The ordering here is important, because the highest numerical value takes
 * precedence when a RTE is specified multiple ways.  See applyLockingClause.
 */
typedef enum LockClauseStrength
{
    LCS_NONE,                   /* no such clause - only used in PlanRowMark
                                 * and ON CONFLICT DO SELECT */
    LCS_FORKEYSHARE,            /* FOR KEY SHARE */
    LCS_FORSHARE,               /* FOR SHARE */
    LCS_FORNOKEYUPDATE,         /* FOR NO KEY UPDATE */
    LCS_FORUPDATE,              /* FOR UPDATE */
} LockClauseStrength;
 
/*
 * This enum controls how to deal with rows being locked by FOR UPDATE/SHARE
 * clauses (i.e., it represents the NOWAIT and SKIP LOCKED options).
 * The ordering here is important, because the highest numerical value takes
 * precedence when a RTE is specified multiple ways.  See applyLockingClause.
 */
typedef enum LockWaitPolicy
{
    /* Wait for the lock to become available (default behavior) */
    LockWaitBlock,
    /* Skip rows that can't be locked (SKIP LOCKED) */
    LockWaitSkip,
    /* Raise an error if a row cannot be locked (NOWAIT) */
    LockWaitError,
} LockWaitPolicy;
 
/*
 * Possible lock modes for a tuple.
 */
typedef enum LockTupleMode
{
    /* SELECT FOR KEY SHARE */
    LockTupleKeyShare,
    /* SELECT FOR SHARE */
    LockTupleShare,
    /* SELECT FOR NO KEY UPDATE, and UPDATEs that don't modify key columns */
    LockTupleNoKeyExclusive,
    /* SELECT FOR UPDATE, UPDATEs that modify key columns, and DELETE */
    LockTupleExclusive,
} LockTupleMode;
 
#endif                          /* LOCKOPTIONS_H */