1 | #pragma once |
2 | |
3 | #include <Columns/IColumn.h> |
4 | #include <DataStreams/IBlockStream_fwd.h> |
5 | |
6 | #include <vector> |
7 | |
8 | |
9 | namespace DB |
10 | { |
11 | class IDictionarySource; |
12 | using DictionarySourcePtr = std::unique_ptr<IDictionarySource>; |
13 | |
14 | /** Data-provider interface for external dictionaries, |
15 | * abstracts out the data source (file, MySQL, ClickHouse, external program, network request et cetera) |
16 | * from the presentation and memory layout (the dictionary itself). |
17 | */ |
18 | class IDictionarySource |
19 | { |
20 | public: |
21 | /// Returns an input stream with all the data available from this source. |
22 | virtual BlockInputStreamPtr loadAll() = 0; |
23 | |
24 | /// Returns an input stream with updated data available from this source. |
25 | virtual BlockInputStreamPtr loadUpdatedAll() = 0; |
26 | |
27 | /** Indicates whether this source supports "random access" loading of data |
28 | * loadId and loadIds can only be used if this function returns true. |
29 | */ |
30 | virtual bool supportsSelectiveLoad() const = 0; |
31 | |
32 | /** Returns an input stream with the data for a collection of identifiers. |
33 | * It must be guaranteed, that 'ids' array will live at least until all data will be read from returned stream. |
34 | */ |
35 | virtual BlockInputStreamPtr loadIds(const std::vector<UInt64> & ids) = 0; |
36 | |
37 | /** Returns an input stream with the data for a collection of composite keys. |
38 | * `requested_rows` contains indices of all rows containing unique keys. |
39 | * It must be guaranteed, that 'requested_rows' array will live at least until all data will be read from returned stream. |
40 | */ |
41 | virtual BlockInputStreamPtr loadKeys(const Columns & key_columns, const std::vector<size_t> & requested_rows) = 0; |
42 | |
43 | /// indicates whether the source has been modified since last load* operation |
44 | virtual bool isModified() const = 0; |
45 | |
46 | /// Returns true if update field is defined |
47 | virtual bool hasUpdateField() const = 0; |
48 | |
49 | virtual DictionarySourcePtr clone() const = 0; |
50 | |
51 | /// returns an informal string describing the source |
52 | virtual std::string toString() const = 0; |
53 | |
54 | virtual ~IDictionarySource() = default; |
55 | }; |
56 | |
57 | } |
58 | |