#pragma once #include #include #include namespace DB { /// Reads the data between pairs of marks in the same part. When reading consecutive ranges, avoids unnecessary seeks. /// When ranges are almost consecutive, seeks are fast because they are performed inside the buffer. /// Avoids loading the marks file if it is not needed (e.g. when reading the whole part). class MergeTreeReaderCompact : public IMergeTreeReader { public: MergeTreeReaderCompact(const MergeTreeData::DataPartPtr & data_part_, const NamesAndTypesList & columns_, UncompressedCache * uncompressed_cache_, MarkCache * mark_cache_, const MarkRanges & mark_ranges_, const ReaderSettings & settings_, const ValueSizeMap & avg_value_size_hints_ = ValueSizeMap{}); /// 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 size_t readRows(size_t from_mark, bool continue_reading, size_t max_rows_to_read, Block & res) override; bool canReadIncompleteGranules() const override { return false; } private: ReadBuffer * data_buffer; std::unique_ptr cached_buffer; std::unique_ptr non_cached_buffer; MergeTreeMarksLoader marks_loader; std::vector> column_positions; size_t next_mark = 0; void initMarksLoader(); void seekToStart(); void seekToMark(size_t row, size_t col); const MarkInCompressedFile & getMark(size_t row, size_t col); void readData(const String & name, const IDataType & type, IColumn & column, size_t from_mark, size_t column_position, size_t rows_to_read); static auto constexpr NAME_OF_FILE_WITH_DATA = "data"; /// Columns that are read. friend class MergeTreeRangeReader::DelayedStream; }; }