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db_include/nodes/lockoptions.h

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+/*-------------------------------------------------------------------------
+ *
+ * lockoptions.h
+ *	  Common header for some locking-related declarations.
+ *
+ *
+ * Copyright (c) 2014-2021, 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 */
+	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 */