Fix tli history file fetching, broken by the archive after crash recevery patch.

If we were about to enter archive recovery after crash recovery, we scanned
the archive for the latest tli history file, and set the recovery target
timeline to that. However, when we actually tried to read the history file,
we would not fetch the file from the archive, because we were not in archive
recovery yet.

To fix, make readTimeLineHistory and existsTimeLineHistory to always fetch
the file from archive if archive recovery is requested, even if we're not in
archive recovery yet.

Backpatch to 9.2. Mitsumasa KONDO

src/backend/access/transam/timeline.c

@@ -92,7 +92,7 @@ readTimeLineHistory(TimeLineID targetTLI)
 		return list_make1(entry);
 	}
 
-	if (InArchiveRecovery)
+	if (ArchiveRecoveryRequested)
 	{
 		TLHistoryFileName(histfname, targetTLI);
 		fromArchive =
@@ -213,7 +213,7 @@ existsTimeLineHistory(TimeLineID probeTLI)
 	if (probeTLI == 1)
 		return false;
 
-	if (InArchiveRecovery)
+	if (ArchiveRecoveryRequested)
 	{
 		TLHistoryFileName(histfname, probeTLI);
 		RestoreArchivedFile(path, histfname, "RECOVERYHISTORY", 0, false);
@@ -316,7 +316,7 @@ writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
 	/*
 	 * If a history file exists for the parent, copy it verbatim
 	 */
-	if (InArchiveRecovery)
+	if (ArchiveRecoveryRequested)
 	{
 		TLHistoryFileName(histfname, parentTLI);
 		RestoreArchivedFile(path, histfname, "RECOVERYHISTORY", 0, false);

src/backend/access/transam/xlog.c

@@ -200,7 +200,7 @@ static int	LocalXLogInsertAllowed = -1;
  * will switch to using offline XLOG archives as soon as we reach the end of
  * WAL in pg_xlog.
 */
-static bool ArchiveRecoveryRequested = false;
+bool ArchiveRecoveryRequested = false;
 bool InArchiveRecovery = false;
 
 /* Was the last xlog file restored from archive, or local? */
@@ -4339,11 +4339,6 @@ readRecoveryCommandFile(void)
 	 */
 	if (rtliGiven)
 	{
-		/*
-		 * Temporarily set InArchiveRecovery, so that existsTimeLineHistory
-		 * or findNewestTimeLine below will check the archive.
-		 */
-		InArchiveRecovery = true;
 		if (rtli)
 		{
 			/* Timeline 1 does not have a history file, all else should */
@@ -4360,7 +4355,6 @@ readRecoveryCommandFile(void)
 			recoveryTargetTLI = findNewestTimeLine(recoveryTargetTLI);
 			recoveryTargetIsLatest = true;
 		}
-		InArchiveRecovery = false;
 	}
 
 	FreeConfigVariables(head);

src/include/access/xlog_internal.h

@@ -263,6 +263,7 @@ extern void GetOldestRestartPoint(XLogRecPtr *oldrecptr, TimeLineID *oldtli);
  * Exported for the functions in timeline.c and xlogarchive.c.  Only valid
  * in the startup process.
  */
+extern bool ArchiveRecoveryRequested;
 extern bool InArchiveRecovery;
 extern bool StandbyMode;
 extern char *recoveryRestoreCommand;