ClickHouse/src/Databases/DatabaseMemory.h
2022-03-20 20:02:15 +01:00

63 lines
2.1 KiB
C++

#pragma once
#include <Databases/DatabasesCommon.h>
#include <Common/escapeForFileName.h>
#include <Parsers/ASTCreateQuery.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 final : public DatabaseWithOwnTablesBase
{
public:
DatabaseMemory(const String & name_, ContextPtr context);
String getEngineName() const override { return "Memory"; }
void createTable(
ContextPtr context,
const String & table_name,
const StoragePtr & table,
const ASTPtr & query) override;
void dropTable(
ContextPtr context,
const String & table_name,
bool no_delay) override;
ASTPtr getCreateTableQueryImpl(const String & name, ContextPtr context, bool throw_on_error) const override;
ASTPtr getCreateDatabaseQuery() const override;
/// DatabaseMemory allows to create tables, which store data on disk.
/// It's needed to create such tables in default database of clickhouse-local.
/// TODO May be it's better to use DiskMemory for such tables.
/// To save data on disk it's possible to explicitly CREATE DATABASE db ENGINE=Ordinary in clickhouse-local.
String getTableDataPath(const String & table_name) const override { return data_path + escapeForFileName(table_name) + "/"; }
String getTableDataPath(const ASTCreateQuery & query) const override { return getTableDataPath(query.getTable()); }
UUID tryGetTableUUID(const String & table_name) const override;
void drop(ContextPtr context) override;
void alterTable(ContextPtr local_context, const StorageID & table_id, const StorageInMemoryMetadata & metadata) override;
/// This database can contain tables to backup.
bool hasTablesToBackup() const override { return true; }
private:
String data_path;
using NameToASTCreate = std::unordered_map<String, ASTPtr>;
NameToASTCreate create_queries;
};
}