[Issue #128] Get timeline ID via pg_control_checkpoint() function

Author: gsmolk

Documentation.md

@@ -245,6 +245,7 @@ GRANT EXECUTE ON FUNCTION pg_catalog.pg_last_xlog_replay_location() TO backup;
 GRANT EXECUTE ON FUNCTION pg_catalog.txid_current() TO backup;
 GRANT EXECUTE ON FUNCTION pg_catalog.txid_current_snapshot() TO backup;
 GRANT EXECUTE ON FUNCTION pg_catalog.txid_snapshot_xmax(txid_snapshot) TO backup;
+GRANT EXECUTE ON FUNCTION pg_catalog.pg_control_checkpoint() TO backup;
 COMMIT;
 ```
 
@@ -263,6 +264,7 @@ GRANT EXECUTE ON FUNCTION pg_catalog.pg_last_wal_replay_lsn() TO backup;
 GRANT EXECUTE ON FUNCTION pg_catalog.txid_current() TO backup;
 GRANT EXECUTE ON FUNCTION pg_catalog.txid_current_snapshot() TO backup;
 GRANT EXECUTE ON FUNCTION pg_catalog.txid_snapshot_xmax(txid_snapshot) TO backup;
+GRANT EXECUTE ON FUNCTION pg_catalog.pg_control_checkpoint() TO backup;
 COMMIT;
 ```
 

src/backup.c

@@ -183,7 +183,13 @@ do_backup_instance(PGconn *backup_conn, PGNodeInfo *nodeInfo)
 	}
 
 	/* Obtain current timeline */
-	current.tli = get_current_timeline(false);
+	current.tli = get_current_timeline(backup_conn);
+
+#if PG_VERSION_NUM >= 90600
+	current.tli = get_current_timeline(backup_conn);
+#else
+	current.tli = get_current_timeline_from_control(false);
+#endif
 
 	/*
 	 * In incremental backup mode ensure that already-validated

src/pg_probackup.h

@@ -788,7 +788,8 @@ extern XLogRecPtr get_first_record_lsn(const char *archivedir, XLogRecPtr start_
 									TimeLineID tli, uint32 wal_seg_size);
 
 /* in util.c */
-extern TimeLineID get_current_timeline(bool safe);
+extern TimeLineID get_current_timeline(PGconn *conn);
+extern TimeLineID get_current_timeline_from_control(bool safe);
 extern XLogRecPtr get_checkpoint_location(PGconn *conn);
 extern uint64 get_system_identifier(const char *pgdata_path);
 extern uint64 get_remote_system_identifier(PGconn *conn);

src/util.c

@@ -146,7 +146,36 @@ writeControlFile(ControlFileData *ControlFile, char *path, fio_location location
  * used by a node.
  */
 TimeLineID
-get_current_timeline(bool safe)
+get_current_timeline(PGconn *conn)
+{
+
+	PGresult   *res;
+	TimeLineID tli = 0;
+	char	   *val;
+
+	res = pgut_execute_extended(conn,
+				   "SELECT timeline_id FROM pg_control_checkpoint()", 0, NULL, true, true);
+
+	if (PQresultStatus(res) == PGRES_TUPLES_OK)
+		val = PQgetvalue(res, 0, 0);
+	else
+		return get_current_timeline_from_control(false);
+
+	if (!parse_uint32(val, &tli, 0))
+	{
+		PQclear(res);
+		elog(WARNING, "Invalid value of timeline_id %s", val);
+
+		/* TODO 3.0 remove it and just error out */
+		return get_current_timeline_from_control(false);
+	}
+
+	return tli;
+}
+
+/* Get timeline from pg_control file */
+TimeLineID
+get_current_timeline_from_control(bool safe)
 {
 	ControlFileData ControlFile;
 	char       *buffer;
@@ -164,6 +193,8 @@ get_current_timeline(bool safe)
 	return ControlFile.checkPointCopy.ThisTimeLineID;
 }
 
+
+
 /*
  * Get last check point record ptr from pg_tonrol.
  */