From 9e8b28131e6a0d272650d1d5268bc767612b1004 Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@yandex-team.ru>
Date: Tue, 15 Sep 2015 00:09:33 +0300
Subject: [PATCH] dbms: fixed error [#METR-17536].

---
 dbms/include/DB/Columns/ColumnAggregateFunction.h | 4 ++--
 dbms/src/Interpreters/Aggregator.cpp              | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/dbms/include/DB/Columns/ColumnAggregateFunction.h b/dbms/include/DB/Columns/ColumnAggregateFunction.h
index 0fc394419f9..68bf2970a4f 100644
--- a/dbms/include/DB/Columns/ColumnAggregateFunction.h
+++ b/dbms/include/DB/Columns/ColumnAggregateFunction.h
@@ -100,9 +100,9 @@ public:
 		arenas.push_back(arena_);
 	}
 
-	ColumnPtr convertToValues()
+	ColumnPtr convertToValues() const
 	{
-		IAggregateFunction * function = holder->func;
+		const IAggregateFunction * function = holder->func;
 		ColumnPtr res = function->getReturnType()->createColumn();
 		IColumn & column = *res;
 		res->reserve(getData().size());
diff --git a/dbms/src/Interpreters/Aggregator.cpp b/dbms/src/Interpreters/Aggregator.cpp
index ce615fb53d4..56ea0ea896e 100644
--- a/dbms/src/Interpreters/Aggregator.cpp
+++ b/dbms/src/Interpreters/Aggregator.cpp
@@ -1756,7 +1756,7 @@ Block Aggregator::mergeBlocks(BlocksList & blocks, bool final)
 
 		for (const auto & block : merged_blocks)
 		{
-			if (block && !block.info.is_overflows)
+			if (block && block.rowsInFirstColumn() && !block.info.is_overflows)
 				has_nonempty_nonoverflows = true;
 			else if (block.info.is_overflows)
 				has_overflows = true;
@@ -1777,7 +1777,7 @@ Block Aggregator::mergeBlocks(BlocksList & blocks, bool final)
 		{
 			for (auto it = merged_blocks.begin(); it != merged_blocks.end(); ++it)
 			{
-				if (!*it)
+				if (!*it || it->rowsInFirstColumn() == 0)
 				{
 					merged_blocks.erase(it);
 					break;