1 | #pragma once |
2 | |
3 | #include <DataTypes/IDataTypeDummy.h> |
4 | |
5 | |
6 | namespace DB |
7 | { |
8 | |
9 | /** Data type that cannot have any values. |
10 | * Used to represent NULL of unknown type as Nullable(Nothing), |
11 | * and possibly for empty array of unknown type as Array(Nothing). |
12 | */ |
13 | class DataTypeNothing final : public IDataTypeDummy |
14 | { |
15 | public: |
16 | static constexpr bool is_parametric = false; |
17 | |
18 | const char * getFamilyName() const override { return "Nothing" ; } |
19 | TypeIndex getTypeId() const override { return TypeIndex::Nothing; } |
20 | |
21 | MutableColumnPtr createColumn() const override; |
22 | |
23 | /// These methods read and write zero bytes just to allow to figure out size of column. |
24 | void serializeBinaryBulk(const IColumn & column, WriteBuffer & ostr, size_t offset, size_t limit) const override; |
25 | void deserializeBinaryBulk(IColumn & column, ReadBuffer & istr, size_t limit, double avg_value_size_hint) const override; |
26 | |
27 | bool equals(const IDataType & rhs) const override; |
28 | |
29 | bool isParametric() const override { return false; } |
30 | bool textCanContainOnlyValidUTF8() const override { return true; } |
31 | bool haveMaximumSizeOfValue() const override { return true; } |
32 | size_t getSizeOfValueInMemory() const override { return 0; } |
33 | bool canBeInsideNullable() const override { return true; } |
34 | }; |
35 | |
36 | } |
37 | |