ClickHouse/src/Interpreters/sortBlock.h
2021-05-08 19:12:31 +03:00

47 lines
1.7 KiB
C++

#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 = nullptr;
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);
}