src/include/nodes/lockoptions.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * lockoptions.h
   4  *        Common header for some locking-related declarations.
   5  *
   6  *
   7  * Copyright (c) 2014-2025, PostgreSQL Global Development Group
   8  *
   9  * src/include/nodes/lockoptions.h
  10  *
  11  *-------------------------------------------------------------------------
  12  */
  13 #ifndef LOCKOPTIONS_H
  14 #define LOCKOPTIONS_H
  15
  16 /*
  17  * This enum represents the different strengths of FOR UPDATE/SHARE clauses.
  18  * The ordering here is important, because the highest numerical value takes
  19  * precedence when a RTE is specified multiple ways.  See applyLockingClause.
  20  */
  21 typedef enum LockClauseStrength
  22 {
  23         LCS_NONE,                                       /* no such clause - only used in PlanRowMark */
  24         LCS_FORKEYSHARE,                        /* FOR KEY SHARE */
  25         LCS_FORSHARE,                           /* FOR SHARE */
  26         LCS_FORNOKEYUPDATE,                     /* FOR NO KEY UPDATE */
  27         LCS_FORUPDATE,                          /* FOR UPDATE */
  28 } LockClauseStrength;
  29
  30 /*
  31  * This enum controls how to deal with rows being locked by FOR UPDATE/SHARE
  32  * clauses (i.e., it represents the NOWAIT and SKIP LOCKED options).
  33  * The ordering here is important, because the highest numerical value takes
  34  * precedence when a RTE is specified multiple ways.  See applyLockingClause.
  35  */
  36 typedef enum LockWaitPolicy
  37 {
  38         /* Wait for the lock to become available (default behavior) */
  39         LockWaitBlock,
  40         /* Skip rows that can't be locked (SKIP LOCKED) */
  41         LockWaitSkip,
  42         /* Raise an error if a row cannot be locked (NOWAIT) */
  43         LockWaitError,
  44 } LockWaitPolicy;
  45
  46 /*
  47  * Possible lock modes for a tuple.
  48  */
  49 typedef enum LockTupleMode
  50 {
  51         /* SELECT FOR KEY SHARE */
  52         LockTupleKeyShare,
  53         /* SELECT FOR SHARE */
  54         LockTupleShare,
  55         /* SELECT FOR NO KEY UPDATE, and UPDATEs that don't modify key columns */
  56         LockTupleNoKeyExclusive,
  57         /* SELECT FOR UPDATE, UPDATEs that modify key columns, and DELETE */
  58         LockTupleExclusive,
  59 } LockTupleMode;
  60
  61 #endif                                                  /* LOCKOPTIONS_H */