1 | #include <Functions/IFunctionImpl.h> |
---|---|
2 | #include <Functions/FunctionFactory.h> |
3 | #include <DataTypes/DataTypeString.h> |
4 | #include <Common/DNSResolver.h> |
5 | #include <Core/Field.h> |
6 | |
7 | |
8 | namespace DB |
9 | { |
10 | |
11 | /// Get the host name. Is is constant on single server, but is not constant in distributed queries. |
12 | class FunctionHostName : public IFunction |
13 | { |
14 | public: |
15 | static constexpr auto name = "hostName"; |
16 | static FunctionPtr create(const Context &) |
17 | { |
18 | return std::make_shared<FunctionHostName>(); |
19 | } |
20 | |
21 | String getName() const override |
22 | { |
23 | return name; |
24 | } |
25 | |
26 | bool isDeterministic() const override { return false; } |
27 | |
28 | bool isDeterministicInScopeOfQuery() const override |
29 | { |
30 | return false; |
31 | } |
32 | |
33 | size_t getNumberOfArguments() const override |
34 | { |
35 | return 0; |
36 | } |
37 | |
38 | DataTypePtr getReturnTypeImpl(const DataTypes & /*arguments*/) const override |
39 | { |
40 | return std::make_shared<DataTypeString>(); |
41 | } |
42 | |
43 | /** convertToFullColumn needed because in distributed query processing, |
44 | * each server returns its own value. |
45 | */ |
46 | void executeImpl(Block & block, const ColumnNumbers &, size_t result, size_t input_rows_count) override |
47 | { |
48 | block.getByPosition(result).column = block.getByPosition(result).type->createColumnConst( |
49 | input_rows_count, DNSResolver::instance().getHostName())->convertToFullColumnIfConst(); |
50 | } |
51 | }; |
52 | |
53 | |
54 | void registerFunctionHostName(FunctionFactory & factory) |
55 | { |
56 | factory.registerFunction<FunctionHostName>(); |
57 | } |
58 | |
59 | } |
60 |