ClickHouse/dbms/include/DB/Dictionaries/DictionaryStructure.h

#pragma once

#include <DB/DataTypes/DataTypeFactory.h>
#include <DB/IO/ReadBufferFromString.h>
#include <DB/IO/WriteBuffer.h>
#include <DB/IO/WriteHelpers.h>
#include <Poco/Util/AbstractConfiguration.h>
#include <ext/range.hpp>
#include <numeric>
#include <vector>
#include <string>
#include <map>
#include <experimental/optional>


namespace DB
{

enum class AttributeUnderlyingType
{
	UInt8,
	UInt16,
	UInt32,
	UInt64,
	Int8,
	Int16,
	Int32,
	Int64,
	Float32,
	Float64,
	String
};


/** Для неявных преобразований в функциях dictGet.
  */
bool isAttributeTypeConvertibleTo(AttributeUnderlyingType from, AttributeUnderlyingType to);

AttributeUnderlyingType getAttributeUnderlyingType(const std::string & type);

std::string toString(const AttributeUnderlyingType type);


/// Min and max lifetimes for a dictionary or it's entry
struct DictionaryLifetime final
{
	UInt64 min_sec;
	UInt64 max_sec;

	DictionaryLifetime(const Poco::Util::AbstractConfiguration & config, const std::string & config_prefix);
};


/** Holds the description of a single dictionary attribute:
*	- name, used for lookup into dictionary and source;
*	- type, used in conjunction with DataTypeFactory and getAttributeUnderlyingTypeByname;
*	- null_value, used as a default value for non-existent entries in the dictionary,
*		decimal representation for numeric attributes;
*	- hierarchical, whether this attribute defines a hierarchy;
*	- injective, whether the mapping to parent is injective (can be used for optimization of GROUP BY?)
*/
struct DictionaryAttribute final
{
	const std::string name;
	const AttributeUnderlyingType underlying_type;
	const DataTypePtr type;
	const std::string expression;
	const Field null_value;
	const bool hierarchical;
	const bool injective;
};


struct DictionarySpecialAttribute final
{
	const std::string name;
	const std::string expression;

	DictionarySpecialAttribute(const Poco::Util::AbstractConfiguration & config, const std::string & config_prefix);
};


/// Name of identifier plus list of attributes
struct DictionaryStructure final
{
	std::experimental::optional<DictionarySpecialAttribute> id;
	std::experimental::optional<std::vector<DictionaryAttribute>> key;
	std::vector<DictionaryAttribute> attributes;
	std::experimental::optional<DictionarySpecialAttribute> range_min;
	std::experimental::optional<DictionarySpecialAttribute> range_max;
	bool has_expressions = false;

	DictionaryStructure(const Poco::Util::AbstractConfiguration & config, const std::string & config_prefix);

	void validateKeyTypes(const DataTypes & key_types) const;
	std::string getKeyDescription() const;
	bool isKeySizeFixed() const;
	std::size_t getKeySize() const;

private:
	std::vector<DictionaryAttribute> getAttributes(
		const Poco::Util::AbstractConfiguration & config, const std::string & config_prefix,
		const bool hierarchy_allowed = true, const bool allow_null_values = true);
};

}