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