[Issue #118]: trust txid_snapshot_xmax() when determining recovery_xid

Author: gsmolk

src/backup.c

@@ -2019,18 +2019,18 @@ pg_stop_backup(pgBackup *backup, PGconn *pg_startbackup_conn,
 			xlog_path = arclog_path;
 
 		backup->stop_lsn = stop_backup_lsn;
+		backup->recovery_xid = recovery_xid;
 
 		elog(LOG, "Getting the Recovery Time from WAL");
 
 		/* iterate over WAL from stop_backup lsn to start_backup lsn */
 		if (!read_recovery_info(xlog_path, backup->tli,
 								instance_config.xlog_seg_size,
 								backup->start_lsn, backup->stop_lsn,
-								&backup->recovery_time, &backup->recovery_xid))
+								&backup->recovery_time))
 		{
 			elog(LOG, "Failed to find Recovery Time in WAL, forced to trust current_timestamp");
 			backup->recovery_time = recovery_time;
-			backup->recovery_xid = recovery_xid;
 		}
 	}
 }

src/parsexlog.c

@@ -425,7 +425,7 @@ validate_wal(pgBackup *backup, const char *archivedir,
 bool
 read_recovery_info(const char *archivedir, TimeLineID tli, uint32 wal_seg_size,
 				   XLogRecPtr start_lsn, XLogRecPtr stop_lsn,
-				   time_t *recovery_time, TransactionId *recovery_xid)
+				   time_t *recovery_time)
 {
 	XLogRecPtr	startpoint = stop_lsn;
 	XLogReaderState *xlogreader;
@@ -472,7 +472,6 @@ read_recovery_info(const char *archivedir, TimeLineID tli, uint32 wal_seg_size,
 		if (getRecordTimestamp(xlogreader, &last_time))
 		{
 			*recovery_time = timestamptz_to_time_t(last_time);
-			*recovery_xid = XLogRecGetXid(xlogreader);
 
 			/* Found timestamp in WAL record 'record' */
 			res = true;

src/pg_probackup.h

@@ -707,8 +707,7 @@ extern void validate_wal(pgBackup *backup, const char *archivedir,
 extern bool read_recovery_info(const char *archivedir, TimeLineID tli,
 							   uint32 seg_size,
 							   XLogRecPtr start_lsn, XLogRecPtr stop_lsn,
-							   time_t *recovery_time,
-							   TransactionId *recovery_xid);
+							   time_t *recovery_time);
 extern bool wal_contains_lsn(const char *archivedir, XLogRecPtr target_lsn,
 							 TimeLineID target_tli, uint32 seg_size);
 extern XLogRecPtr get_prior_record_lsn(const char *archivedir, XLogRecPtr start_lsn,