ClickHouse/src/Storages/ReadInOrderOptimizer.h
2020-06-17 14:05:11 +03:00

33 lines
918 B
C++

#pragma once
#include <Core/SortDescription.h>
#include <Storages/MergeTree/MergeTreeData.h>
#include <Storages/SelectQueryInfo.h>
namespace DB
{
/** Helper class, that can analyze MergeTree order key
* and required sort description to get their
* common prefix, which is needed for
* performing reading in order of PK.
*/
class ReadInOrderOptimizer
{
public:
ReadInOrderOptimizer(
const ManyExpressionActions & elements_actions,
const SortDescription & required_sort_description,
const SyntaxAnalyzerResultPtr & syntax_result);
InputOrderInfoPtr getInputOrder(const StoragePtr & storage, const StorageMetadataPtr & metadata_snapshot) const;
private:
/// Actions for every element of order expression to analyze functions for monotonicity
ManyExpressionActions elements_actions;
NameSet forbidden_columns;
SortDescription required_sort_description;
};
}