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127 lines
4.2 KiB
C++
127 lines
4.2 KiB
C++
#pragma once
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#include <Core/Types.h>
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#include <Core/NamesAndTypes.h>
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#include <Storages/ColumnDefault.h>
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#include <ctime>
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#include <memory>
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#include <functional>
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class ThreadPool;
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namespace DB
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{
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class Context;
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class IStorage;
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using StoragePtr = std::shared_ptr<IStorage>;
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class IAST;
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using ASTPtr = std::shared_ptr<IAST>;
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struct Settings;
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/** Allows to iterate over tables.
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*/
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class IDatabaseIterator
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{
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public:
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virtual void next() = 0;
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virtual bool isValid() const = 0;
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virtual const String & name() const = 0;
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virtual StoragePtr & table() const = 0;
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virtual ~IDatabaseIterator() {}
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};
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using DatabaseIteratorPtr = std::unique_ptr<IDatabaseIterator>;
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/** Database engine.
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* It is responsible for:
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* - initialization of set of known tables;
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* - checking existence of a table and getting a table object;
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* - retrieving a list of all tables;
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* - creating and dropping tables;
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* - renaming tables and moving between databases with same engine.
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*/
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class IDatabase : public std::enable_shared_from_this<IDatabase>
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{
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public:
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/// Get name of database engine.
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virtual String getEngineName() const = 0;
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/// Load a set of existing tables. If thread_pool is specified, use it.
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/// You can call only once, right after the object is created.
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virtual void loadTables(Context & context, ThreadPool * thread_pool, bool has_force_restore_data_flag) = 0;
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/// Check the existence of the table.
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virtual bool isTableExist(const String & name) const = 0;
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/// Get the table for work. Return nullptr if there is no table.
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virtual StoragePtr tryGetTable(const String & name) = 0;
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/// Get an iterator that allows you to pass through all the tables.
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/// It is possible to have "hidden" tables that are not visible when passing through, but are visible if you get them by name using the functions above.
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virtual DatabaseIteratorPtr getIterator() = 0;
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/// Is the database empty.
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virtual bool empty() const = 0;
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/// Add the table to the database. Record its presence in the metadata.
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virtual void createTable(
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const String & name, const StoragePtr & table, const ASTPtr & query, const String & engine, const Settings & settings) = 0;
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/// Delete the table from the database and return it. Delete the metadata.
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virtual void removeTable(const String & name) = 0;
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/// Add a table to the database, but do not add it to the metadata. The database may not support this method.
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virtual void attachTable(const String & name, const StoragePtr & table) = 0;
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/// Forget about the table without deleting it, and return it. The database may not support this method.
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virtual StoragePtr detachTable(const String & name) = 0;
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/// Rename the table and possibly move the table to another database.
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virtual void renameTable(
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const Context & context, const String & name, IDatabase & to_database, const String & to_name, const Settings & settings) = 0;
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/// Returns time of table's metadata change, 0 if there is no corresponding metadata file.
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virtual time_t getTableMetadataModificationTime(const String & name) = 0;
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using ASTModifier = std::function<void(ASTPtr &)>;
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/// Change the table structure in metadata.
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/// You must call under the TableStructureLock of the corresponding table . If engine_modifier is empty, then engine does not change.
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virtual void alterTable(
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const Context & context,
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const String & name,
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const NamesAndTypesList & columns,
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const NamesAndTypesList & materialized_columns,
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const NamesAndTypesList & alias_columns,
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const ColumnDefaults & column_defaults,
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const ASTModifier & engine_modifier) = 0;
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/// Get the CREATE TABLE query for the table. It can also provide information for detached tables for which there is metadata.
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virtual ASTPtr getCreateQuery(const String & name) const = 0;
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/// Ask all tables to complete the background threads they are using and delete all table objects.
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virtual void shutdown() = 0;
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/// Delete metadata, the deletion of which differs from the recursive deletion of the directory, if any.
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virtual void drop() = 0;
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virtual ~IDatabase() {}
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};
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using DatabasePtr = std::shared_ptr<IDatabase>;
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using Databases = std::map<String, DatabasePtr>;
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}
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