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

#pragma once

#include <DB/Dictionaries/IDictionarySource.h>
#include <DB/Dictionaries/DictionaryStructure.h>
#include <DB/Dictionaries/ExternalQueryBuilder.h>
#include <DB/Client/ConnectionPool.h>
#include <Poco/Util/AbstractConfiguration.h>
#include <memory>


namespace DB
{

/** Allows loading dictionaries from local or remote ClickHouse instance
  *	@todo use ConnectionPoolWithFailover
  *	@todo invent a way to keep track of source modifications
  */
class ClickHouseDictionarySource final : public IDictionarySource
{
public:
	ClickHouseDictionarySource(const DictionaryStructure & dict_struct_,
		const Poco::Util::AbstractConfiguration & config,
		const std::string & config_prefix,
		const Block & sample_block, Context & context);

	/// copy-constructor is provided in order to support cloneability
	ClickHouseDictionarySource(const ClickHouseDictionarySource & other);

	BlockInputStreamPtr loadAll() override;

	BlockInputStreamPtr loadIds(const std::vector<UInt64> & ids) override;

	BlockInputStreamPtr loadKeys(
		const ConstColumnPlainPtrs & key_columns, const std::vector<size_t> & requested_rows) override;

	bool isModified() const override { return true; }
	bool supportsSelectiveLoad() const override { return true; }

	DictionarySourcePtr clone() const override { return std::make_unique<ClickHouseDictionarySource>(*this); }

	std::string toString() const override;

private:
	BlockInputStreamPtr createStreamForSelectiveLoad(const std::string query);

	const DictionaryStructure dict_struct;
	const std::string host;
	const UInt16 port;
	const std::string user;
	const std::string password;
	const std::string db;
	const std::string table;
	const std::string where;
	ExternalQueryBuilder query_builder;
	Block sample_block;
	Context & context;
	const bool is_local;
	ConnectionPoolPtr pool;
	const std::string load_all_query;
};

}