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

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#pragma once
#include <ext/shared_ptr_helper.hpp>
#include <DB/Core/NamesAndTypes.h>
#include <DB/Storages/IStorage.h>
#include <DB/DataStreams/NullBlockInputStream.h>
#include <DB/DataStreams/NullBlockOutputStream.h>
namespace DB
{
/** При записи, ничего не делает.
* При чтении, возвращает пустоту.
*/
class StorageNull : private ext::shared_ptr_helper<StorageNull>, public IStorage
{
friend class ext::shared_ptr_helper<StorageNull>;
public:
static StoragePtr create(
const std::string & name_,
NamesAndTypesListPtr columns_,
const NamesAndTypesList & materialized_columns_,
const NamesAndTypesList & alias_columns_,
const ColumnDefaults & column_defaults_)
{
return make_shared(name_, columns_, materialized_columns_, alias_columns_, column_defaults_);
}
std::string getName() const override { return "Null"; }
std::string getTableName() const override { return name; }
const NamesAndTypesList & getColumnsListImpl() const override { return *columns; }
BlockInputStreams read(
const Names & column_names,
ASTPtr query,
const Context & context,
const Settings & settings,
QueryProcessingStage::Enum & processed_stage,
const size_t max_block_size = DEFAULT_BLOCK_SIZE,
const unsigned threads = 1) override
{
return { std::make_shared<NullBlockInputStream>() };
}
BlockOutputStreamPtr write(ASTPtr query, const Settings & settings) override
{
return std::make_shared<NullBlockOutputStream>();
}
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;
StorageNull(
const std::string & name_,
NamesAndTypesListPtr columns_,
const NamesAndTypesList & materialized_columns_,
const NamesAndTypesList & alias_columns_,
const ColumnDefaults & column_defaults_)
: IStorage{materialized_columns_, alias_columns_, column_defaults_}, name(name_), columns(columns_) {}
};
}