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#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 ASTSelectQuery & query,
const ManyExpressionActions & elements_actions,
const SortDescription & required_sort_description,
const TreeRewriterResultPtr & syntax_result);
InputOrderInfoPtr getInputOrder(const StorageMetadataPtr & metadata_snapshot, ContextPtr context, UInt64 limit = 0) const;
private:
InputOrderInfoPtr getInputOrderImpl(
const StorageMetadataPtr & metadata_snapshot,
const SortDescription & description,
const ManyExpressionActions & actions,
const ContextPtr & context,
UInt64 limit) const;
/// Actions for every element of order expression to analyze functions for monotonicity
ManyExpressionActions elements_actions;
NameSet forbidden_columns;
NameToNameMap array_join_result_to_source;
SortDescription required_sort_description;
const ASTSelectQuery & query;
};
}
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