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#pragma once
#include <Storages/MergeTree/MergeTreeBaseSelectProcessor.h>
namespace DB
{
class IMergeTreeReadPool;
using IMergeTreeReadPoolPtr = std::shared_ptr<IMergeTreeReadPool>;
/** Used in conjunction with MergeTreeReadPool, asking it for more work to do and performing whatever reads it is asked
* to perform.
*/
class MergeTreeThreadSelectAlgorithm final : public IMergeTreeSelectAlgorithm
{
public:
MergeTreeThreadSelectAlgorithm(
size_t thread_,
IMergeTreeReadPoolPtr pool_,
size_t min_marks_for_concurrent_read,
size_t max_block_size_,
size_t preferred_block_size_bytes_,
size_t preferred_max_column_in_block_size_bytes_,
const MergeTreeData & storage_,
const StorageSnapshotPtr & storage_snapshot_,
bool use_uncompressed_cache_,
const PrewhereInfoPtr & prewhere_info_,
const ExpressionActionsSettings & actions_settings_,
const MergeTreeReaderSettings & reader_settings_,
const Names & virt_column_names_);
String getName() const override { return "MergeTreeThread"; }
~MergeTreeThreadSelectAlgorithm() override;
protected:
/// Requests read task from MergeTreeReadPool and signals whether it got one
bool getNewTaskImpl() override;
void finalizeNewTask() override;
void finish() override;
private:
/// "thread" index (there are N threads and each thread is assigned index in interval [0..N-1])
size_t thread;
IMergeTreeReadPoolPtr pool;
/// Last part read in this thread
std::string last_read_part_name;
};
}
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