Fix pg_recvlogical avoidance of superfluous Standby Status Update.

The defect suppressed a Standby Status Update message when bytes flushed
to disk had changed but bytes received had not changed.  If
pg_recvlogical then exited with no intervening Standby Status Update,
the next pg_recvlogical repeated already-flushed records.  The defect
could also cause superfluous messages, which are functionally harmless.
Back-patch to 9.5 (all supported versions).

Discussion: https://postgr.es/m/20200502221647.GA3941274@rfd.leadboat.com

diff --git a/src/bin/pg_basebackup/pg_recvlogical.c b/src/bin/pg_basebackup/pg_recvlogical.c
index 5907d607b094d3868c891dd53d2c89f5d3af1189..7101f5fd51544cdc15b36c6f6bfc36b6aab03bdc 100644 (file)
--- a/src/bin/pg_basebackup/pg_recvlogical.c
+++ b/src/bin/pg_basebackup/pg_recvlogical.c
@@ -121,7 +121,7 @@ sendFeedback(PGconn *conn, int64 now, bool force, bool replyRequested)
         */
        if (!force &&
                last_written_lsn == output_written_lsn &&
-               last_fsync_lsn != output_fsync_lsn)
+               last_fsync_lsn == output_fsync_lsn)
                return true;
 
        if (verbose)