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[email protected]

diff --git a/src/bin/pg_basebackup/pg_recvlogical.c b/src/bin/pg_basebackup/pg_recvlogical.c
index a5f90b2d6264a322bf17ee2584d7bbdaab56c79c..adb9f800c71a1b1b57d63692c02f73c2a61b8810 100644 (file)
--- a/src/bin/pg_basebackup/pg_recvlogical.c
+++ b/src/bin/pg_basebackup/pg_recvlogical.c
@@ -127,7 +127,7 @@ sendFeedback(PGconn *conn, TimestampTz 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)