fix-excessive-walreceiver-fsyncing.patch

diff --git a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
index 5aac85d..9e8504b 100644
--- a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
+++ b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
@@ -351,28 +351,33 @@ libpqrcv_receive(int timeout, unsigned char *type, char **buffer, int *len)
 		PQfreemem(recvBuf);
 	recvBuf = NULL;
 
-	/*
-	 * If the caller requested to block, wait for data to arrive. But if this
-	 * is the first call after connecting, don't wait, because there might
-	 * already be some data in libpq buffer that we haven't returned to
-	 * caller.
-	 */
-	if (timeout > 0 && !justconnected)
+	/* Try to receive a CopyData message */
+	rawlen = PQgetCopyData(streamConn, &recvBuf, 1);
+	if (rawlen == 0)
 	{
-		if (!libpq_select(timeout))
-			return false;
+		/*
+		 * No data available yet. If the caller requested to block, wait for
+		 * more data to arrive. But if this is the first call after connecting,
+		 * don't wait, because there might already be some data in libpq buffer
+		 * that we haven't returned to caller.
+		 */
+		if (timeout > 0 && !justconnected)
+		{
+			if (!libpq_select(timeout))
+				return false;
+		}
+		justconnected = false;
 
 		if (PQconsumeInput(streamConn) == 0)
 			ereport(ERROR,
 					(errmsg("could not receive data from WAL stream: %s",
 							PQerrorMessage(streamConn))));
-	}
-	justconnected = false;
 
-	/* Receive CopyData message */
-	rawlen = PQgetCopyData(streamConn, &recvBuf, 1);
-	if (rawlen == 0)			/* no data available yet, then return */
-		return false;
+		/* Now that we've consumed some input, try again */
+		rawlen = PQgetCopyData(streamConn, &recvBuf, 1);
+		if (rawlen == 0)
+			return false;
+	}
 	if (rawlen == -1)			/* end-of-streaming or error */
 	{
 		PGresult   *res;