mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-10-18 22:40:50 +00:00
54 lines
1.8 KiB
C++
54 lines
1.8 KiB
C++
#pragma once
|
|
|
|
#include <Parsers/ASTSelectQuery.h>
|
|
#include <Interpreters/DatabaseAndTableWithAlias.h>
|
|
|
|
namespace DB
|
|
{
|
|
|
|
class Context;
|
|
struct Settings;
|
|
|
|
/** Predicate optimization based on rewriting ast rules
|
|
* For more details : https://github.com/ClickHouse/ClickHouse/pull/2015#issuecomment-374283452
|
|
* The optimizer does two different optimizations
|
|
* - Move predicates from having to where
|
|
* - Push the predicate down from the current query to the having of the subquery
|
|
*/
|
|
class PredicateExpressionsOptimizer
|
|
{
|
|
public:
|
|
PredicateExpressionsOptimizer(const Context & context_, const TablesWithColumnNames & tables_with_columns_, const Settings & settings_);
|
|
|
|
bool optimize(ASTSelectQuery & select_query);
|
|
|
|
private:
|
|
/// Extracts settings, mostly to show which are used and which are not.
|
|
struct ExtractedSettings
|
|
{
|
|
const bool enable_optimize_predicate_expression;
|
|
const bool enable_optimize_predicate_expression_to_final_subquery;
|
|
|
|
template<typename T>
|
|
ExtractedSettings(const T & settings_)
|
|
: enable_optimize_predicate_expression(settings_.enable_optimize_predicate_expression),
|
|
enable_optimize_predicate_expression_to_final_subquery(settings_.enable_optimize_predicate_expression_to_final_subquery)
|
|
{}
|
|
};
|
|
|
|
const Context & context;
|
|
const std::vector<TableWithColumnNames> & tables_with_columns;
|
|
|
|
const ExtractedSettings settings;
|
|
|
|
std::vector<ASTs> extractTablesPredicates(const ASTPtr & where, const ASTPtr & prewhere);
|
|
|
|
bool tryRewritePredicatesToTables(ASTs & tables_element, const std::vector<ASTs> & tables_predicates);
|
|
|
|
bool tryRewritePredicatesToTable(ASTPtr & table_element, const ASTs & table_predicates, const Names & table_column) const;
|
|
|
|
bool tryMovePredicatesFromHavingToWhere(ASTSelectQuery & select_query);
|
|
};
|
|
|
|
}
|