ClickHouse/dbms/src/Interpreters/sortBlock.h

#pragma once

#include <Core/Block.h>
#include <Core/SortDescription.h>


namespace DB
{

/// Sort one block by `description`. If limit != 0, then the partial sort of the first `limit` rows is produced.
void sortBlock(Block & block, const SortDescription & description, UInt64 limit = 0);


/** Used only in StorageMergeTree to sort the data with INSERT.
  * Sorting is stable. This is important for keeping the order of rows in the CollapsingMergeTree engine
  *  - because based on the order of rows it is determined whether to delete or leave groups of rows when collapsing.
  * Collations are not supported. Partial sorting is not supported.
  */
void stableSortBlock(Block & block, const SortDescription & description);

/** Same as stableSortBlock, but do not sort the block, but only calculate the permutation of the values,
  *  so that you can rearrange the column values yourself.
  */
void stableGetPermutation(const Block & block, const SortDescription & description, IColumn::Permutation & out_permutation);


/** Quickly check whether the block is already sorted. If the block is not sorted - returns false as fast as possible.
  * Collations are not supported.
  */
bool isAlreadySorted(const Block & block, const SortDescription & description);

/// Column with description for sort
struct ColumnWithSortDescription
{
    const IColumn * column;
    SortColumnDescription description;

    /// It means, that this column is ColumnConst
    bool column_const = false;
};

using ColumnsWithSortDescriptions = std::vector<ColumnWithSortDescription>;

ColumnsWithSortDescriptions getColumnsWithSortDescription(const Block & block, const SortDescription & description);

}