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99 lines
3.8 KiB
C++
99 lines
3.8 KiB
C++
#pragma once
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#include <Core/NamesAndTypes.h>
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#include <Storages/MergeTree/IMergeTreeReader.h>
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#include <IO/ReadBufferFromFileBase.h>
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namespace DB
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{
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class MergeTreeDataPartCompact;
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using DataPartCompactPtr = std::shared_ptr<const MergeTreeDataPartCompact>;
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class IMergeTreeDataPart;
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using DataPartPtr = std::shared_ptr<const IMergeTreeDataPart>;
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/// Reader for compact parts
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class MergeTreeReaderCompact : public IMergeTreeReader
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{
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public:
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MergeTreeReaderCompact(
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MergeTreeDataPartInfoForReaderPtr data_part_info_for_read_,
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NamesAndTypesList columns_,
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const VirtualFields & virtual_fields_,
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const StorageSnapshotPtr & storage_snapshot_,
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UncompressedCache * uncompressed_cache_,
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MarkCache * mark_cache_,
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MarkRanges mark_ranges_,
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MergeTreeReaderSettings settings_,
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ThreadPool * load_marks_threadpool_,
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ValueSizeMap avg_value_size_hints_ = {},
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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.
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/// 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, size_t current_task_last_mark,
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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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void prefetchBeginOfRange(Priority priority) override;
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private:
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bool isContinuousReading(size_t mark, size_t column_position);
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void fillColumnPositions();
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void initialize();
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ReadBuffer * data_buffer;
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CompressedReadBufferBase * compressed_data_buffer;
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std::unique_ptr<CachedCompressedReadBuffer> cached_buffer;
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std::unique_ptr<CompressedReadBufferFromFile> non_cached_buffer;
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MergeTreeMarksLoader marks_loader;
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/// Storage columns with collected separate arrays of Nested to columns of Nested type.
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/// They maybe be needed for finding offsets of missed Nested columns in parts.
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/// They are rarely used and are heavy to initialized, so we create them
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/// only on demand and cache in this field.
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std::optional<ColumnsDescription> storage_columns_with_collected_nested;
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/// Positions of columns in part structure.
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using ColumnPositions = std::vector<std::optional<size_t>>;
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ColumnPositions column_positions;
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/// Should we read full column or only it's offsets.
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/// Element of the vector is the level of the alternative stream.
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std::vector<ColumnNameLevel> columns_for_offsets;
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/// For asynchronous reading from remote fs. Same meaning as in MergeTreeReaderStream.
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std::optional<size_t> last_right_offset;
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size_t next_mark = 0;
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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 NameAndTypePair & name_and_type, ColumnPtr & column, size_t from_mark,
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size_t current_task_last_mark, size_t column_position,
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size_t rows_to_read, ColumnNameLevel name_level_for_offsets, std::unordered_map<String, ColumnPtr> & columns_cache_for_subcolumns);
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/// Returns maximal value of granule size in compressed file from @mark_ranges.
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/// This value is used as size of read buffer.
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static size_t getReadBufferSize(
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const IMergeTreeDataPartInfoForReader & data_part_info_for_reader,
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MergeTreeMarksLoader & marks_loader,
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const ColumnPositions & column_positions,
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const MarkRanges & mark_ranges);
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/// For asynchronous reading from remote fs.
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void adjustUpperBound(size_t last_mark);
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ReadBufferFromFileBase::ProfileCallback profile_callback;
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clockid_t clock_type;
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bool initialized = false;
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};
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}
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