ClickHouse/src/Storages/MergeTree/MergeTreeReaderCompact.h

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#pragma once
#include <Core/NamesAndTypes.h>
#include <Storages/MergeTree/IMergeTreeReader.h>
namespace DB
{
class MergeTreeDataPartCompact;
using DataPartCompactPtr = std::shared_ptr<const MergeTreeDataPartCompact>;
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/// Reader for compact parts
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class MergeTreeReaderCompact : public IMergeTreeReader
{
public:
MergeTreeReaderCompact(
DataPartCompactPtr data_part_,
NamesAndTypesList columns_,
const StorageMetadataPtr & metadata_snapshot_,
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UncompressedCache * uncompressed_cache_,
MarkCache * mark_cache_,
MarkRanges mark_ranges_,
MergeTreeReaderSettings settings_,
ValueSizeMap avg_value_size_hints_ = {},
const ReadBufferFromFileBase::ProfileCallback & profile_callback_ = {},
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clockid_t clock_type_ = CLOCK_MONOTONIC_COARSE);
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/// Return the number of rows has been read or zero if there is no columns to read.
/// If continue_reading is true, continue reading from last state, otherwise seek to from_mark
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size_t readRows(size_t from_mark, bool continue_reading, size_t max_rows_to_read, Columns & res_columns) override;
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bool canReadIncompleteGranules() const override { return false; }
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private:
bool isContinuousReading(size_t mark, size_t column_position);
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ReadBuffer * data_buffer;
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std::unique_ptr<CachedCompressedReadBuffer> cached_buffer;
std::unique_ptr<CompressedReadBufferFromFile> non_cached_buffer;
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MergeTreeMarksLoader marks_loader;
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/// Positions of columns in part structure.
std::vector<ColumnPosition> column_positions;
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/// Should we read full column or only it's offsets
std::vector<bool> read_only_offsets;
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size_t next_mark = 0;
std::optional<std::pair<size_t, size_t>> last_read_granule;
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void seekToMark(size_t row_index, size_t column_index);
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void readData(const String & name, IColumn & column, const IDataType & type,
size_t from_mark, size_t column_position, size_t rows_to_read, bool only_offsets = false);
size_t getReadBufferSize();
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};
}