Little better [#CLICKHOUSE-4].

dbms/src/Columns/ColumnNullable.cpp

@@ -14,6 +14,7 @@ namespace ErrorCodes
 {
     extern const int LOGICAL_ERROR;
     extern const int ILLEGAL_COLUMN;
+    extern const int SIZES_OF_NESTED_COLUMNS_ARE_INCONSISTENT;
 }
 
 
@@ -448,4 +449,12 @@ void ColumnNullable::applyNullMap(const ColumnNullable & other)
     applyNullMap(other.getNullMapConcreteColumn());
 }
 
+
+void ColumnNullable::checkConsistency() const
+{
+    if (null_map->size() != nested_column->size())
+        throw Exception("Logical error: Sizes of nested column and null map of Nullable column are not equal",
+            ErrorCodes::SIZES_OF_NESTED_COLUMNS_ARE_INCONSISTENT);
+}
+
 }

dbms/src/Columns/ColumnNullable.h

@@ -90,6 +90,9 @@ public:
     void applyNullMap(const ColumnUInt8 & map);
     void applyNegatedNullMap(const ColumnUInt8 & map);
 
+    /// Check that size of null map equals to size of nested column.
+    void checkConsistency() const;
+
 private:
     ColumnPtr nested_column;
     ColumnPtr null_map;

dbms/src/Core/ErrorCodes.cpp

@@ -368,6 +368,7 @@ namespace ErrorCodes
     extern const int CANNOT_CREATE_IO_BUFFER = 363;
     extern const int RECEIVED_ERROR_TOO_MANY_REQUESTS = 364;
     extern const int OUTPUT_IS_NOT_SORTED = 365;
+    extern const int SIZES_OF_NESTED_COLUMNS_ARE_INCONSISTENT = 366;
 
     extern const int KEEPER_EXCEPTION = 999;
     extern const int POCO_EXCEPTION = 1000;

dbms/src/DataTypes/DataTypeNullable.cpp

@@ -20,6 +20,7 @@ DataTypeNullable::DataTypeNullable(DataTypePtr nested_data_type_)
 void DataTypeNullable::serializeBinaryBulk(const IColumn & column, WriteBuffer & ostr, size_t offset, size_t limit) const
 {
     const ColumnNullable & col = static_cast<const ColumnNullable &>(column);
+    col.checkConsistency();
     nested_data_type->serializeBinaryBulk(*col.getNestedColumn(), ostr, offset, limit);
 }