From 75dc9db388ab64f4deb73475b5e074c6898c10f6 Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@yandex-team.ru>
Date: Fri, 27 Mar 2015 02:48:50 +0300
Subject: [PATCH] dbms: ALTER: writing to log just before waiting for lock
 [#METR-2944].

---
 dbms/src/Storages/StorageReplicatedMergeTree.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/dbms/src/Storages/StorageReplicatedMergeTree.cpp b/dbms/src/Storages/StorageReplicatedMergeTree.cpp
index f99732892d9..9024008b801 100644
--- a/dbms/src/Storages/StorageReplicatedMergeTree.cpp
+++ b/dbms/src/Storages/StorageReplicatedMergeTree.cpp
@@ -1467,6 +1467,8 @@ void StorageReplicatedMergeTree::alterThread()
 			/// Если описание столбцов изменилось, обновим структуру таблицы локально.
 			if (changed_version)
 			{
+				LOG_INFO(log, "Changed version of 'columns' node in ZooKeeper. Waiting for structure write lock.");
+
 				auto table_lock = lockStructureForAlter();
 
 				const auto columns_changed = columns != data.getColumnsListNonMaterialized();