Merge pull request #7689 from ClickHouse/constants-and-remote

Fix remote constants.

(cherry picked from commit 2233660)

dbms/src/DataStreams/RemoteBlockInputStream.cpp

@@ -2,6 +2,7 @@
 #include <DataStreams/OneBlockInputStream.h>
 #include <Common/NetException.h>
 #include <Common/CurrentThread.h>
+#include <Columns/ColumnConst.h>
 #include <Interpreters/Context.h>
 #include <Interpreters/castColumn.h>
 #include <Interpreters/InternalTextLogsQueue.h>
@@ -173,9 +174,30 @@ static Block adaptBlockStructure(const Block & block, const Block & header, cons
         ColumnPtr column;
 
         if (elem.column && isColumnConst(*elem.column))
-            /// TODO: check that column from block contains the same value.
-            /// TODO: serialize const columns.
-            column = elem.column->cloneResized(block.rows());
+        {
+            /// We expect constant column in block.
+            /// If block is not empty, then get value for constant from it,
+            /// because it may be different for remote server for functions like version(), uptime(), ...
+            if (block.rows() > 0 && block.has(elem.name))
+            {
+                /// Const column is passed as materialized. Get first value from it.
+                ///
+                /// TODO: check that column contains the same value.
+                /// TODO: serialize const columns.
+                auto col = block.getByName(elem.name);
+                col.column = block.getByName(elem.name).column->cut(0, 1);
+
+                column = castColumn(col, elem.type, context);
+
+                if (!isColumnConst(*column))
+                    column = ColumnConst::create(column, block.rows());
+                else
+                    /// It is not possible now. Just in case we support const columns serialization.
+                    column = column->cloneResized(block.rows());
+            }
+            else
+                column = elem.column->cloneResized(block.rows());
+        }
         else
             column = castColumn(block.getByName(elem.name), elem.type, context);
 

dbms/tests/integration/test_replicating_constants/test.py

@@ -0,0 +1,21 @@
+import pytest
+
+from helpers.cluster import ClickHouseCluster
+
+cluster = ClickHouseCluster(__file__)
+
+node1 = cluster.add_instance('node1', with_zookeeper=True)
+node2 = cluster.add_instance('node2', with_zookeeper=True, image='yandex/clickhouse-server:19.1.14', with_installed_binary=True)
+
+@pytest.fixture(scope="module")
+def start_cluster():
+    try:
+        cluster.start()
+
+        yield cluster
+    finally:
+        cluster.shutdown()
+
+def test_different_versions(start_cluster):
+
+    assert node1.query("SELECT uniqExact(x) FROM (SELECT version() as x from remote('node{1,2}', system.one))") == "2\n"