1 files changed, 98 insertions, 0 deletions
diff --git a/src/include/access/xlogwait.h b/src/include/access/xlogwait.h
new file mode 100644
index 00000000000..4dc328b1b07
--- /dev/null
+++ b/src/include/access/xlogwait.h
@@ -0,0 +1,98 @@
+/*-------------------------------------------------------------------------
+ *
+ * xlogwait.h
+ *	  Declarations for LSN replay waiting routines.
+ *
+ * Copyright (c) 2025, PostgreSQL Global Development Group
+ *
+ * src/include/access/xlogwait.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef XLOG_WAIT_H
+#define XLOG_WAIT_H
+
+#include "access/xlogdefs.h"
+#include "lib/pairingheap.h"
+#include "port/atomics.h"
+#include "storage/procnumber.h"
+#include "storage/spin.h"
+#include "tcop/dest.h"
+
+/*
+ * Result statuses for WaitForLSNReplay().
+ */
+typedef enum
+{
+	WAIT_LSN_RESULT_SUCCESS,	/* Target LSN is reached */
+	WAIT_LSN_RESULT_NOT_IN_RECOVERY,	/* Recovery ended before or during our
+										 * wait */
+	WAIT_LSN_RESULT_TIMEOUT		/* Timeout occurred */
+} WaitLSNResult;
+
+/*
+ * LSN type for waiting facility.
+ */
+typedef enum WaitLSNType
+{
+	WAIT_LSN_TYPE_REPLAY = 0,	/* Waiting for replay on standby */
+	WAIT_LSN_TYPE_FLUSH = 1,	/* Waiting for flush on primary */
+	WAIT_LSN_TYPE_COUNT = 2
+} WaitLSNType;
+
+/*
+ * WaitLSNProcInfo - the shared memory structure representing information
+ * about the single process, which may wait for LSN operations.  An item of
+ * waitLSNState->procInfos array.
+ */
+typedef struct WaitLSNProcInfo
+{
+	/* LSN, which this process is waiting for */
+	XLogRecPtr	waitLSN;
+
+	/* Process to wake up once the waitLSN is reached */
+	ProcNumber	procno;
+
+	/* Heap membership flags for LSN types */
+	bool		inHeap[WAIT_LSN_TYPE_COUNT];
+
+	/* Heap nodes for LSN types */
+	pairingheap_node heapNode[WAIT_LSN_TYPE_COUNT];
+} WaitLSNProcInfo;
+
+/*
+ * WaitLSNState - the shared memory state for the LSN waiting facility.
+ */
+typedef struct WaitLSNState
+{
+	/*
+	 * The minimum LSN values some process is waiting for.  Used for the
+	 * fast-path checking if we need to wake up any waiters after replaying a
+	 * WAL record.  Could be read lock-less.  Update protected by WaitLSNLock.
+	 */
+	pg_atomic_uint64 minWaitedLSN[WAIT_LSN_TYPE_COUNT];
+
+	/*
+	 * A pairing heaps of waiting processes ordered by LSN values (least LSN
+	 * is on top).  Protected by WaitLSNLock.
+	 */
+	pairingheap waitersHeap[WAIT_LSN_TYPE_COUNT];
+
+	/*
+	 * An array with per-process information, indexed by the process number.
+	 * Protected by WaitLSNLock.
+	 */
+	WaitLSNProcInfo procInfos[FLEXIBLE_ARRAY_MEMBER];
+} WaitLSNState;
+
+
+extern PGDLLIMPORT WaitLSNState *waitLSNState;
+
+extern Size WaitLSNShmemSize(void);
+extern void WaitLSNShmemInit(void);
+extern void WaitLSNWakeup(WaitLSNType lsnType, XLogRecPtr currentLSN);
+extern void WaitLSNCleanup(void);
+extern WaitLSNResult WaitForLSN(WaitLSNType lsnType, XLogRecPtr targetLSN,
+								int64 timeout);
+
+#endif							/* XLOG_WAIT_H */