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40 lines
1.4 KiB
C++
40 lines
1.4 KiB
C++
#pragma once
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#include <Storages/MergeTree/IMergedBlockOutputStream.h>
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namespace DB
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{
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/// Writes only those columns that are in `header`
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class MergedColumnOnlyOutputStream final : public IMergedBlockOutputStream
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{
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public:
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/// skip_offsets: used when ALTERing columns if we know that array offsets are not altered.
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/// Pass empty 'already_written_offset_columns' first time then and pass the same object to subsequent instances of MergedColumnOnlyOutputStream
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/// if you want to serialize elements of Nested data structure in different instances of MergedColumnOnlyOutputStream.
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MergedColumnOnlyOutputStream(
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MergeTreeData & storage_, const Block & header_, const String & part_path_, bool sync_,
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CompressionCodecPtr default_codec_, bool skip_offsets_,
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const std::vector<MergeTreeIndexPtr> & indices_to_recalc_,
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WrittenOffsetColumns & already_written_offset_columns_,
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const MergeTreeIndexGranularity & index_granularity_,
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const MergeTreeIndexGranularityInfo * index_granularity_info_ = nullptr);
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Block getHeader() const override { return header; }
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void write(const Block & block) override;
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void writeSuffix() override;
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MergeTreeData::DataPart::Checksums writeSuffixAndGetChecksums();
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private:
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Block header;
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bool sync;
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bool skip_offsets;
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/// To correctly write Nested elements column-by-column.
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WrittenOffsetColumns & already_written_offset_columns;
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};
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}
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