clickhouse: sleep function not sleeping on empty blocks [#CONV-2807].

dbms/include/DB/Functions/FunctionsMiscellaneous.h

@@ -409,30 +409,32 @@ public:
 	{
 		IColumn * col = &*block.getByPosition(arguments[0]).column;
 		double seconds;
-		size_t size;
+		size_t size = col->size();
 		
 		if (ColumnConst<Float64> * column = dynamic_cast<ColumnConst<Float64> *>(col))
-			size = column->size(), seconds = column->getData();
+			seconds = column->getData();
 		
 		else if (ColumnConst<Float32> * column = dynamic_cast<ColumnConst<Float32> *>(col))
-			size = column->size(), seconds = static_cast<double>(column->getData());
+			seconds = static_cast<double>(column->getData());
 		
 		else if (ColumnConst<UInt64> * column = dynamic_cast<ColumnConst<UInt64> *>(col))
-			size = column->size(), seconds = static_cast<double>(column->getData());
+			seconds = static_cast<double>(column->getData());
 		
 		else if (ColumnConst<UInt32> * column = dynamic_cast<ColumnConst<UInt32> *>(col))
-			size = column->size(), seconds = static_cast<double>(column->getData());
+			seconds = static_cast<double>(column->getData());
 		
 		else if (ColumnConst<UInt16> * column = dynamic_cast<ColumnConst<UInt16> *>(col))
-			size = column->size(), seconds = static_cast<double>(column->getData());
+			seconds = static_cast<double>(column->getData());
 		
 		else if (ColumnConst<UInt8> * column = dynamic_cast<ColumnConst<UInt8> *>(col))
-			size = column->size(), seconds = static_cast<double>(column->getData());
+			seconds = static_cast<double>(column->getData());
 		
 		else
 			throw Exception("The argument of function " + getName() + " must be constant.", ErrorCodes::ILLEGAL_COLUMN);
 		
-		usleep(static_cast<unsigned>(seconds * 1e6));
+		/// Не спим, если блок пустой.
+		if (size > 0)
+			usleep(static_cast<unsigned>(seconds * 1e6));
 		
 		block.getByPosition(result).column = ColumnConst<UInt8>(size, 0).convertToFullColumn();
 	}