ClickHouse/dbms/src/Storages/MergeTree/MergeTreeSharder.h

#pragma once

#include <IO/WriteBufferFromFile.h>
#include <IO/CompressedWriteBuffer.h>
#include <Columns/ColumnsNumber.h>
#include <Interpreters/sortBlock.h>
#include <Storages/MergeTree/MergeTreeData.h>
#include <Core/Block.h>

namespace DB
{

struct ShardedBlockWithDateInterval final
{
    ShardedBlockWithDateInterval(const Block & block_, size_t shard_no_, UInt16 min_date_, UInt16 max_date_);
    ShardedBlockWithDateInterval(const ShardedBlockWithDateInterval &) = delete;
    ShardedBlockWithDateInterval & operator=(const ShardedBlockWithDateInterval &) = delete;

    Block block;
    size_t shard_no;
    UInt16 min_date;
    UInt16 max_date;
};

using ShardedBlocksWithDateIntervals = std::list<ShardedBlockWithDateInterval>;

struct ReshardingJob;

/** Creates new shard parts of data.
  */
class MergeTreeSharder final
{
public:
    MergeTreeSharder(MergeTreeData & data_, const ReshardingJob & job_);
    MergeTreeSharder(const MergeTreeSharder &) = delete;
    MergeTreeSharder & operator=(const MergeTreeSharder &) = delete;

    /** Breaks the block into blocks by the sharding key, each of which
      * must be written to a separate part. It works deterministically: if
      * give the same block to the input, the output will be the same blocks in the
      * in the same order.
      */
    ShardedBlocksWithDateIntervals shardBlock(const Block & block);

private:
    IColumn::Selector createSelector(Block block);

    MergeTreeData & data;
    const ReshardingJob & job;
    Logger * log;
    std::vector<size_t> slots;
    ExpressionActionsPtr sharding_key_expr;
    std::string sharding_key_column_name;
};

}