ClickHouse/dbms/src/Storages/StorageNull.h

57 lines
1.5 KiB
C++

#pragma once
#include <ext/shared_ptr_helper.h>
#include <Core/NamesAndTypes.h>
#include <Storages/IStorage.h>
#include <DataStreams/NullBlockInputStream.h>
#include <DataStreams/NullBlockOutputStream.h>
namespace DB
{
/** When writing, does nothing.
* When reading, returns nothing.
*/
class StorageNull : public ext::shared_ptr_helper<StorageNull>, public IStorage
{
public:
std::string getName() const override { return "Null"; }
std::string getTableName() const override { return table_name; }
BlockInputStreams read(
const Names & column_names,
const SelectQueryInfo &,
const Context & /*context*/,
QueryProcessingStage::Enum /*processing_stage*/,
size_t,
unsigned) override
{
return { std::make_shared<NullBlockInputStream>(getSampleBlockForColumns(column_names)) };
}
BlockOutputStreamPtr write(const ASTPtr &, const Settings &) override
{
return std::make_shared<NullBlockOutputStream>(getSampleBlock());
}
void rename(const String & /*new_path_to_db*/, const String & /*new_database_name*/, const String & new_table_name) override
{
table_name = new_table_name;
}
void alter(const AlterCommands & params, const String & database_name, const String & table_name, const Context & context) override;
private:
String table_name;
protected:
StorageNull(String table_name_, ColumnsDescription columns_description_)
: IStorage{std::move(columns_description_)}, table_name(std::move(table_name_))
{
}
};
}