ClickHouse/dbms/src/Core/BlockInfo.h

#pragma once

#include <Core/Types.h>


namespace DB
{

class ReadBuffer;
class WriteBuffer;

/** More information about the block.
  */
struct BlockInfo
{
    /** is_overflows:
      * After running GROUP BY ... WITH TOTALS with the max_rows_to_group_by and group_by_overflow_mode = 'any' settings,
      *  a row is inserted in the separate block with aggregated values ​​that have not passed max_rows_to_group_by.
      * If it is such a block, then is_overflows is set to true for it.
      */

    /** bucket_num:
      * When using the two-level aggregation method, data with different key groups are scattered across different buckets.
      * In this case, the bucket number is indicated here. It is used to optimize the merge for distributed aggregation.
      * Otherwise -1.
      */

#define APPLY_FOR_BLOCK_INFO_FIELDS(M) \
    M(bool,     is_overflows,     false,     1) \
    M(Int32,    bucket_num,     -1,     2)

#define DECLARE_FIELD(TYPE, NAME, DEFAULT, FIELD_NUM) \
    TYPE NAME = DEFAULT;

    APPLY_FOR_BLOCK_INFO_FIELDS(DECLARE_FIELD)

#undef DECLARE_FIELD

    /// Write the values ​​in binary form. NOTE: You could use protobuf, but it would be overkill for this case.
    void write(WriteBuffer & out) const;

    /// Read the values ​​in binary form.
    void read(ReadBuffer & in);
};

}