1 | #pragma once |
2 | |
3 | #include <Storages/MergeTree/IMergedBlockOutputStream.h> |
4 | |
5 | namespace DB |
6 | { |
7 | |
8 | /// Writes only those columns that are in `header` |
9 | class MergedColumnOnlyOutputStream final : public IMergedBlockOutputStream |
10 | { |
11 | public: |
12 | /// skip_offsets: used when ALTERing columns if we know that array offsets are not altered. |
13 | /// Pass empty 'already_written_offset_columns' first time then and pass the same object to subsequent instances of MergedColumnOnlyOutputStream |
14 | /// if you want to serialize elements of Nested data structure in different instances of MergedColumnOnlyOutputStream. |
15 | MergedColumnOnlyOutputStream( |
16 | MergeTreeData & storage_, const Block & , const String & part_path_, bool sync_, |
17 | CompressionCodecPtr default_codec_, bool skip_offsets_, |
18 | const std::vector<MergeTreeIndexPtr> & indices_to_recalc_, |
19 | WrittenOffsetColumns & already_written_offset_columns_, |
20 | const MergeTreeIndexGranularity & index_granularity_, |
21 | const MergeTreeIndexGranularityInfo * index_granularity_info_ = nullptr); |
22 | |
23 | Block getHeader() const override { return header; } |
24 | void write(const Block & block) override; |
25 | void writeSuffix() override; |
26 | MergeTreeData::DataPart::Checksums writeSuffixAndGetChecksums(); |
27 | |
28 | private: |
29 | Block header; |
30 | |
31 | bool sync; |
32 | bool skip_offsets; |
33 | |
34 | /// To correctly write Nested elements column-by-column. |
35 | WrittenOffsetColumns & already_written_offset_columns; |
36 | }; |
37 | |
38 | |
39 | } |
40 | |