ClickHouse/dbms/include/DB/Storages/StorageMemory.h

#pragma once

#include <Poco/Mutex.h>

#include <DB/Core/NamesAndTypes.h>
#include <DB/Storages/IStorage.h>
#include <DB/DataStreams/IProfilingBlockInputStream.h>
#include <DB/DataStreams/IBlockOutputStream.h>


namespace DB
{

class StorageMemory;

class MemoryBlockInputStream : public IProfilingBlockInputStream
{
public:
	MemoryBlockInputStream(const Names & column_names_, BlocksList::iterator begin_, BlocksList::iterator end_);
	String getName() const { return "MemoryBlockInputStream"; }

	String getID() const
	{
		std::stringstream res;
		res << "Memory(" << &*begin << ", " << &*end;

		for (const auto & name : column_names)
			res << ", " << name;

		res << ")";
		return res.str();
	}

protected:
	Block readImpl();
private:
	Names column_names;
	BlocksList::iterator begin;
	BlocksList::iterator end;
	BlocksList::iterator it;
};


class MemoryBlockOutputStream : public IBlockOutputStream
{
public:
	MemoryBlockOutputStream(StorageMemory & storage_);
	void write(const Block & block);
private:
	StorageMemory & storage;
};


/** Реализует хранилище в оперативке.
  * Подходит для временных данных.
  * В нём не поддерживаются ключи.
  * Данные хранятся в виде набора блоков и никуда дополнительно не сохраняются.
  */
class StorageMemory : public IStorage
{
friend class MemoryBlockInputStream;
friend class MemoryBlockOutputStream;

public:
	static StoragePtr create(
		const std::string & name_,
		NamesAndTypesListPtr columns_);

	static StoragePtr create(
		const std::string & name_,
		NamesAndTypesListPtr columns_,
		const NamesAndTypesList & materialized_columns_,
		const NamesAndTypesList & alias_columns_,
		const ColumnDefaults & column_defaults_);

	std::string getName() const override { return "Memory"; }
	std::string getTableName() const override { return name; }

	const NamesAndTypesList & getColumnsListImpl() const override { return *columns; }

	size_t getSize() const { return data.size(); }

	BlockInputStreams read(
		const Names & column_names,
		ASTPtr query,
		const Context & context,
		const Settings & settings,
		QueryProcessingStage::Enum & processed_stage,
		size_t max_block_size = DEFAULT_BLOCK_SIZE,
		unsigned threads = 1) override;

	BlockOutputStreamPtr write(ASTPtr query) override;

	void drop() override;
	void rename(const String & new_path_to_db, const String & new_database_name, const String & new_table_name) override { name = new_table_name; }

private:
	String name;
	NamesAndTypesListPtr columns;

	/// Сами данные. list - чтобы при вставке в конец, существующие итераторы не инвалидировались.
	BlocksList data;

	Poco::FastMutex mutex;

	StorageMemory(
		const std::string & name_,
		NamesAndTypesListPtr columns_);

	StorageMemory(
		const std::string & name_,
		NamesAndTypesListPtr columns_,
		const NamesAndTypesList & materialized_columns_,
		const NamesAndTypesList & alias_columns_,
		const ColumnDefaults & column_defaults_);
};

}