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 1304b277bc3aa8a16358bc2e01653325c10fd57a..cc8616844ba19bf116d13c57792335d7b6372755 100644 (file)
--- a/src/bin/pg_basebackup/pg_recvlogical.c
+++ b/src/bin/pg_basebackup/pg_recvlogical.c
@@ -126,7 +126,7 @@ 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)