postgres
diff --git a/‎doc/src/sgml/ref/pg_rewind.sgml
Lines changed: 11 additions & 7 deletions b/‎doc/src/sgml/ref/pg_rewind.sgml
Lines changed: 11 additions & 7 deletions
diff --git a/‎src/bin/pg_rewind/Makefile
Lines changed: 1 addition & 1 deletion b/‎src/bin/pg_rewind/Makefile
Lines changed: 1 addition & 1 deletion
diff --git a/‎src/bin/pg_rewind/parsexlog.c
Lines changed: 27 additions & 12 deletions b/‎src/bin/pg_rewind/parsexlog.c
Lines changed: 27 additions & 12 deletions
@@ -61,13 +61,17 @@ PostgreSQL documentation
    <application>pg_rewind</> examines the timeline histories of the source
    and target clusters to determine the point where they diverged, and
    expects to find WAL in the target cluster's <filename>pg_xlog</> directory
-   reaching all the way back to the point of divergence. In the typical
-   failover scenario where the target cluster was shut down soon after the
-   divergence, that is not a problem, but if the target cluster had run for a
-   long time after the divergence, the old WAL files might not be present
-   anymore. In that case, they can be manually copied from the WAL archive to
-   the <filename>pg_xlog</> directory. Fetching missing files from a WAL
-   archive automatically is currently not supported.
+   reaching all the way back to the point of divergence. The point of divergence
+   could be found either on target timeline, source timeline or their common
+   ancestor. In the typical failover scenario where the target cluster was
+   shut down soon after the divergence, that is not a problem, but if the
+   target cluster had run for a long time after the divergence, the old WAL
+   files might not be present anymore. In that case, they can be manually
+   copied from the WAL archive to the <filename>pg_xlog</> directory. Fetching
+   missing files from a WAL archive automatically is currently not supported.
+   Besides, <application>pg_rewind</> use cases are not limited by failover.
+   For instance, standby server could be promoted, run some writes and
+   then be returned back as stanby. 
   </para>
 
   <para>
 
@@ -8,7 +8,7 @@
 #
 #-------------------------------------------------------------------------
 
-PGFILEDESC = "pg_rewind - repurpose an old master server as standby"
+PGFILEDESC = "pg_rewind - synchronize a data directory with another one forked from"
 PGAPPICON = win32
 
 subdir = src/bin/pg_rewind
 
@@ -45,7 +45,7 @@ static char xlogfpath[MAXPGPATH];
 typedef struct XLogPageReadPrivate
 {
 	const char *datadir;
-	TimeLineID	tli;
+	int			tliIndex;
 } XLogPageReadPrivate;
 
 static int SimpleXLogPageRead(XLogReaderState *xlogreader,
@@ -55,11 +55,11 @@ static int SimpleXLogPageRead(XLogReaderState *xlogreader,
 
 /*
  * Read WAL from the datadir/pg_xlog, starting from 'startpoint' on timeline
- * 'tli', until 'endpoint'. Make note of the data blocks touched by the WAL
- * records, and return them in a page map.
+ * index 'tliIndex' in target timeline history, until 'endpoint'. Make note of
  */
 void
-extractPageMap(const char *datadir, XLogRecPtr startpoint, TimeLineID tli,
+extractPageMap(const char *datadir, XLogRecPtr startpoint, int tliIndex,
 			   XLogRecPtr endpoint)
 {
 	XLogRecord *record;
@@ -68,7 +68,7 @@ extractPageMap(const char *datadir, XLogRecPtr startpoint, TimeLineID tli,
 	XLogPageReadPrivate private;
 
 	private.datadir = datadir;
-	private.tli = tli;
+	private.tliIndex = tliIndex;
 	xlogreader = XLogReaderAllocate(&SimpleXLogPageRead, &private);
 	if (xlogreader == NULL)
 		pg_fatal("out of memory\n");
@@ -112,7 +112,7 @@ extractPageMap(const char *datadir, XLogRecPtr startpoint, TimeLineID tli,
  * doing anything with the record itself.
  */
 XLogRecPtr
-readOneRecord(const char *datadir, XLogRecPtr ptr, TimeLineID tli)
+readOneRecord(const char *datadir, XLogRecPtr ptr, int tliIndex)
 {
 	XLogRecord *record;
 	XLogReaderState *xlogreader;
@@ -121,7 +121,7 @@ readOneRecord(const char *datadir, XLogRecPtr ptr, TimeLineID tli)
 	XLogRecPtr	endptr;
 
 	private.datadir = datadir;
-	private.tli = tli;
+	private.tliIndex = tliIndex;
 	xlogreader = XLogReaderAllocate(&SimpleXLogPageRead, &private);
 	if (xlogreader == NULL)
 		pg_fatal("out of memory\n");
@@ -152,7 +152,7 @@ readOneRecord(const char *datadir, XLogRecPtr ptr, TimeLineID tli)
  * Find the previous checkpoint preceding given WAL position.
  */
 void
-findLastCheckpoint(const char *datadir, XLogRecPtr forkptr, TimeLineID tli,
+findLastCheckpoint(const char *datadir, XLogRecPtr forkptr, int tliIndex,
 				   XLogRecPtr *lastchkptrec, TimeLineID *lastchkpttli,
 				   XLogRecPtr *lastchkptredo)
 {
@@ -173,7 +173,7 @@ findLastCheckpoint(const char *datadir, XLogRecPtr forkptr, TimeLineID tli,
 		forkptr += (forkptr % XLogSegSize == 0) ? SizeOfXLogLongPHD : SizeOfXLogShortPHD;
 
 	private.datadir = datadir;
-	private.tli = tli;
+	private.tliIndex = tliIndex;
 	xlogreader = XLogReaderAllocate(&SimpleXLogPageRead, &private);
 	if (xlogreader == NULL)
 		pg_fatal("out of memory\n");
@@ -236,9 +236,11 @@ SimpleXLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr,
 {
 	XLogPageReadPrivate *private = (XLogPageReadPrivate *) xlogreader->private_data;
 	uint32		targetPageOff;
-	XLogSegNo targetSegNo PG_USED_FOR_ASSERTS_ONLY;
+	XLogRecPtr	targetSegEnd;
+	XLogSegNo	targetSegNo;
 
 	XLByteToSeg(targetPagePtr, targetSegNo);
+	XLogSegNoOffsetToRecPtr(targetSegNo + 1, 0, targetSegEnd);
 	targetPageOff = targetPagePtr % XLogSegSize;
 
 	/*
@@ -257,7 +259,20 @@ SimpleXLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr,
 	{
 		char		xlogfname[MAXFNAMELEN];
 
-		XLogFileName(xlogfname, private->tli, xlogreadsegno);
+		/*
+		 * Since incomplete segments are copied into next timelines, switch to
+		 * the timeline holding the required segment. Assuming this scan can be
+		 * done both forward and backward, consider also switching timeline
+		 * accordingly.
+		 */
+		while (private->tliIndex < targetNentries - 1 &&
+				targetHistory[private->tliIndex].end < targetSegEnd)
+			private->tliIndex++;
+		while (private->tliIndex > 0 &&
+				targetHistory[private->tliIndex].begin >= targetSegEnd)
+			private->tliIndex--;
+
+		XLogFileName(xlogfname, targetHistory[private->tliIndex].tli, xlogreadsegno);
 
 		snprintf(xlogfpath, MAXPGPATH, "%s/" XLOGDIR "/%s", private->datadir, xlogfname);
 
@@ -293,7 +308,7 @@ SimpleXLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr,
 
 	Assert(targetSegNo == xlogreadsegno);
 
-	*pageTLI = private->tli;
+	*pageTLI = targetHistory[private->tliIndex].tli;
 	return XLOG_BLCKSZ;
 }