ClickHouse/dbms/src/Databases/DatabaseMemory.h

#pragma once

#include <mutex>
#include <Databases/IDatabase.h>
#include <Storages/IStorage.h>


namespace Poco { class Logger; }


namespace DB
{

/** A non-persistent database to store temporary data.
  * It doesn't make any manipulations with filesystem.
  * All tables are created by calling code.
  * TODO: Maybe DatabaseRuntime is more suitable class name.
  */
class DatabaseMemory : public IDatabase
{
protected:
    const String name;
    mutable std::mutex mutex;
    Tables tables;

    Poco::Logger * log;

public:

    DatabaseMemory(const String & name_) : name(name_) {}

    String getEngineName() const override { return "Memory"; }

    void loadTables(
        Context & context,
        ThreadPool * thread_pool,
        bool has_force_restore_data_flag) override;

    bool empty(const Context & context) const override;

    DatabaseIteratorPtr getIterator(const Context & context) override;

    bool isTableExist(
        const Context & context,
        const String & table_name) const override;

    StoragePtr tryGetTable(
        const Context & context,
        const String & table_name) const override;

    void createTable(
        const Context & context,
        const String & table_name,
        const StoragePtr & table,
        const ASTPtr & query) override;

    void removeTable(
        const Context & context,
        const String & table_name) override;

    void attachTable(const String & table_name, const StoragePtr & table) override;
    StoragePtr detachTable(const String & table_name) override;

    void renameTable(
        const Context & context,
        const String & table_name,
        IDatabase & to_database,
        const String & to_table_name) override;

    void alterTable(
        const Context & context,
        const String & name,
        const NamesAndTypesList & columns,
        const NamesAndTypesList & materialized_columns,
        const NamesAndTypesList & alias_columns,
        const ColumnDefaults & column_defaults,
        const ASTModifier & engine_modifier) override;

    time_t getTableMetadataModificationTime(
        const Context & context,
        const String & table_name) override;

    ASTPtr getCreateQuery(
        const Context & context,
        const String & table_name) const override;

    void shutdown() override;
    void drop() override;
};

}