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#pragma once
#include <Core/NamesAndTypes.h>
#include <Storages/MergeTree/IMergeTreeReader.h>
namespace DB
{
class MergeTreeDataPartWide;
using DataPartWidePtr = std::shared_ptr<const MergeTreeDataPartWide>;
/// Reader for Wide parts.
class MergeTreeReaderWide : public IMergeTreeReader
{
public:
MergeTreeReaderWide(
MergeTreeDataPartInfoForReaderPtr data_part_info_for_read_,
NamesAndTypesList columns_,
const StorageSnapshotPtr & storage_snapshot_,
UncompressedCache * uncompressed_cache_,
MarkCache * mark_cache_,
MarkRanges mark_ranges_,
MergeTreeReaderSettings settings_,
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 true; }
void prefetchBeginOfRange(Priority priority) override;
using FileStreams = std::map<std::string, std::unique_ptr<MergeTreeReaderStream>>;
private:
FileStreams streams;
void prefetchForAllColumns(Priority priority, size_t num_columns, size_t from_mark, size_t current_task_last_mark, bool continue_reading);
void addStreams(
const NameAndTypePair & name_and_type,
const SerializationPtr & serialization,
const ReadBufferFromFileBase::ProfileCallback & profile_callback,
clockid_t clock_type);
void readData(
const NameAndTypePair & name_and_type, const SerializationPtr & serialization, ColumnPtr & column,
size_t from_mark, bool continue_reading, size_t current_task_last_mark, size_t max_rows_to_read,
ISerialization::SubstreamsCache & cache, bool was_prefetched);
/// Make next readData more simple by calling 'prefetch' of all related ReadBuffers (column streams).
void prefetchForColumn(
Priority priority,
const NameAndTypePair & name_and_type,
const SerializationPtr & serialization,
size_t from_mark,
bool continue_reading,
size_t current_task_last_mark,
ISerialization::SubstreamsCache & cache);
void deserializePrefix(
const SerializationPtr & serialization,
const NameAndTypePair & name_and_type,
size_t current_task_last_mark,
ISerialization::SubstreamsCache & cache);
std::unordered_map<String, ISerialization::SubstreamsCache> caches;
std::unordered_set<std::string> prefetched_streams;
ssize_t prefetched_from_mark = -1;
};
}
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