diff --git a/dbms/include/DB/Client/Connection.h b/dbms/include/DB/Client/Connection.h
index ab9fab5c06b..ae38abc2839 100644
--- a/dbms/include/DB/Client/Connection.h
+++ b/dbms/include/DB/Client/Connection.h
@@ -109,7 +109,7 @@ public:
 	bool poll(size_t timeout_microseconds = 0);
 
 	/// Проверить, есть ли данные в буфере для чтения.
-	bool hasReadBufferPendingData();
+	bool hasReadBufferPendingData() const;
 
 	/// Получить пакет от сервера.
 	Packet receivePacket();
diff --git a/dbms/include/DB/IO/ReadBuffer.h b/dbms/include/DB/IO/ReadBuffer.h
index 48e4ab60c8e..d3175042fc4 100644
--- a/dbms/include/DB/IO/ReadBuffer.h
+++ b/dbms/include/DB/IO/ReadBuffer.h
@@ -144,9 +144,9 @@ public:
 	}
 
 	/** Проверить, есть ли данные в буфере для чтения. */
-	bool hasPendingData()
+	bool hasPendingData() const
 	{
-		return offset() != buffer().size();
+		return offset() != working_buffer.size();
 	}
 
 private:
diff --git a/dbms/include/DB/Storages/MergeTree/PartsWithRangesSplitter.h b/dbms/include/DB/Storages/MergeTree/PartsWithRangesSplitter.h
index 4945e991803..a12a4f2c4a9 100644
--- a/dbms/include/DB/Storages/MergeTree/PartsWithRangesSplitter.h
+++ b/dbms/include/DB/Storages/MergeTree/PartsWithRangesSplitter.h
@@ -5,6 +5,8 @@
 namespace DB
 {
 
+using Segments = std::vector<MergeTreeDataSelectExecutor::RangesInDataParts>;
+
 /** Этот класс разбивает объект типа RangesInDataParts (см. MergeTreeDataSelectExecutor)
   * на не больше, чем указанное количество сегментов.
   */
@@ -18,7 +20,7 @@ public:
 	PartsWithRangesSplitter(const PartsWithRangesSplitter &) = delete;
 	PartsWithRangesSplitter & operator=(const PartsWithRangesSplitter &) = delete;
 
-	std::vector<MergeTreeDataSelectExecutor::RangesInDataParts> perform();
+	Segments perform();
 
 private:
 	void init();
@@ -35,11 +37,11 @@ private:
 	// Входные данные.
 	const MergeTreeDataSelectExecutor::RangesInDataParts & input;
 	MergeTreeDataSelectExecutor::RangesInDataParts::const_iterator input_part;
-	std::vector<MarkRange>::const_iterator input_range;
+	MarkRanges::const_iterator input_range;
 
 	// Выходные данные.
-	std::vector<MergeTreeDataSelectExecutor::RangesInDataParts> output_segments;
-	std::vector<MergeTreeDataSelectExecutor::RangesInDataParts>::iterator current_output_segment;
+	Segments output_segments;
+	Segments::iterator current_output_segment;
 	MergeTreeDataSelectExecutor::RangesInDataPart * current_output_part;
 
 	size_t total_size;
diff --git a/dbms/src/Client/Connection.cpp b/dbms/src/Client/Connection.cpp
index 2ab93f91b1d..059c27f5c8e 100644
--- a/dbms/src/Client/Connection.cpp
+++ b/dbms/src/Client/Connection.cpp
@@ -360,9 +360,9 @@ bool Connection::poll(size_t timeout_microseconds)
 }
 
 
-bool Connection::hasReadBufferPendingData()
+bool Connection::hasReadBufferPendingData() const
 {
-	return static_cast<ReadBufferFromPocoSocket &>(*in).hasPendingData();
+	return static_cast<const ReadBufferFromPocoSocket &>(*in).hasPendingData();
 }
 
 
diff --git a/dbms/src/Storages/MergeTree/MergeTreeDataSelectExecutor.cpp b/dbms/src/Storages/MergeTree/MergeTreeDataSelectExecutor.cpp
index c93aed31bda..27a1e950009 100644
--- a/dbms/src/Storages/MergeTree/MergeTreeDataSelectExecutor.cpp
+++ b/dbms/src/Storages/MergeTree/MergeTreeDataSelectExecutor.cpp
@@ -15,10 +15,10 @@
 namespace
 {
 
-std::pair<UInt64, UInt64> computeHash(const DB::MergeTreeDataSelectExecutor::RangesInDataParts & cluster)
+std::pair<UInt64, UInt64> computeHash(const DB::MergeTreeDataSelectExecutor::RangesInDataParts & segment)
 {
 	SipHash hash;
-	for (const auto & part_with_ranges : cluster)
+	for (const auto & part_with_ranges : segment)
 	{
 		const auto & part = *(part_with_ranges.data_part);
 		hash.update(part.name.c_str(), part.name.length());
diff --git a/dbms/src/Storages/MergeTree/PartsWithRangesSplitter.cpp b/dbms/src/Storages/MergeTree/PartsWithRangesSplitter.cpp
index e9322f7d58f..2f2e4304575 100644
--- a/dbms/src/Storages/MergeTree/PartsWithRangesSplitter.cpp
+++ b/dbms/src/Storages/MergeTree/PartsWithRangesSplitter.cpp
@@ -29,13 +29,13 @@ PartsWithRangesSplitter::PartsWithRangesSplitter(const MergeTreeDataSelectExecut
 	}
 	total_size *= granularity;
 
-	if ((total_size == 0) || (min_segment_size == 0) || (max_segments_count < 2))
+	if ((granularity == 0) || (min_segment_size == 0) || (max_segments_count == 0) || (total_size == 0))
 		throw Exception("One or more arguments are invalid.", ErrorCodes::BAD_ARGUMENTS);
 }
 
-std::vector<MergeTreeDataSelectExecutor::RangesInDataParts> PartsWithRangesSplitter::perform()
+Segments PartsWithRangesSplitter::perform()
 {
-	if (total_size > min_segment_size)
+	if ((max_segments_count > 1) && (total_size > min_segment_size))
 	{
 		init();
 		while (emitRange()) {}