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diff --git a/src/include/access/timeline.h b/src/include/access/timeline.h
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+/*
+ * timeline.h
+ *
+ * Functions for reading and writing timeline history files.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/timeline.h
+ */
+#ifndef TIMELINE_H
+#define TIMELINE_H
+
+#include "access/xlogdefs.h"
+#include "nodes/pg_list.h"
+
+/*
+ * A list of these structs describes the timeline history of the server. Each
+ * TimeLineHistoryEntry represents a piece of WAL belonging to the history,
+ * from newest to oldest. All WAL locations between 'begin' and 'end' belong to
+ * the timeline represented by the entry. Together the 'begin' and 'end'
+ * pointers of all the entries form a contiguous line from beginning of time
+ * to infinity.
+ */
+typedef struct
+{
+	TimeLineID	tli;
+	XLogRecPtr	begin;			/* inclusive */
+	XLogRecPtr	end;			/* exclusive, InvalidXLogRecPtr means infinity */
+} TimeLineHistoryEntry;
+
+extern List *readTimeLineHistory(TimeLineID targetTLI);
+extern bool existsTimeLineHistory(TimeLineID probeTLI);
+extern TimeLineID findNewestTimeLine(TimeLineID startTLI);
+extern void writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
+								 XLogRecPtr switchpoint, char *reason);
+extern void writeTimeLineHistoryFile(TimeLineID tli, char *content, int size);
+extern void restoreTimeLineHistoryFiles(TimeLineID begin, TimeLineID end);
+extern bool tliInHistory(TimeLineID tli, List *expectedTLEs);
+extern TimeLineID tliOfPointInHistory(XLogRecPtr ptr, List *history);
+extern XLogRecPtr tliSwitchPoint(TimeLineID tli, List *history,
+								 TimeLineID *nextTLI);
+
+#endif							/* TIMELINE_H */