From c7b94c70e87b45758c0c6268fcb38e4c1294842e Mon Sep 17 00:00:00 2001
From: Alexander Kuzmenkov <akuzm@yandex-team.ru>
Date: Tue, 21 Jan 2020 20:45:44 +0300
Subject: [PATCH] Fix sending no data to client with Null format.

Looks like before it could only work accidentally due to some mighty
NRVO.
---
 dbms/src/DataStreams/BlockIO.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/dbms/src/DataStreams/BlockIO.h b/dbms/src/DataStreams/BlockIO.h
index 50af2922306..c043e297d1f 100644
--- a/dbms/src/DataStreams/BlockIO.h
+++ b/dbms/src/DataStreams/BlockIO.h
@@ -66,6 +66,8 @@ struct BlockIO
         finish_callback         = rhs.finish_callback;
         exception_callback      = rhs.exception_callback;
 
+        null_format             = rhs.null_format;
+
         return *this;
     }
 };