1 | #pragma once |
2 | |
3 | #include <ext/shared_ptr_helper.h> |
4 | #include <Storages/IStorage.h> |
5 | |
6 | |
7 | namespace DB |
8 | { |
9 | |
10 | class Context; |
11 | |
12 | |
13 | /** Implements storage for the system table One. |
14 | * The table contains a single column of dummy UInt8 and a single row with a value of 0. |
15 | * Used when the table is not specified in the query. |
16 | * Analog of the DUAL table in Oracle and MySQL. |
17 | */ |
18 | class StorageSystemOne : public ext::shared_ptr_helper<StorageSystemOne>, public IStorage |
19 | { |
20 | friend struct ext::shared_ptr_helper<StorageSystemOne>; |
21 | public: |
22 | std::string getName() const override { return "SystemOne" ; } |
23 | std::string getTableName() const override { return name; } |
24 | std::string getDatabaseName() const override { return "system" ; } |
25 | |
26 | BlockInputStreams read( |
27 | const Names & column_names, |
28 | const SelectQueryInfo & query_info, |
29 | const Context & context, |
30 | QueryProcessingStage::Enum processed_stage, |
31 | size_t max_block_size, |
32 | unsigned num_streams) override; |
33 | |
34 | private: |
35 | const std::string name; |
36 | |
37 | protected: |
38 | StorageSystemOne(const std::string & name_); |
39 | }; |
40 | |
41 | } |
42 | |