mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-13 11:04:10 +00:00
49 lines
1.3 KiB
C++
49 lines
1.3 KiB
C++
#pragma once
|
||
|
||
#include <DB/Storages/IStorage.h>
|
||
#include <DB/DataStreams/IProfilingBlockInputStream.h>
|
||
|
||
|
||
namespace DB
|
||
{
|
||
|
||
|
||
class OneValueBlockInputStream : public IProfilingBlockInputStream
|
||
{
|
||
public:
|
||
OneValueBlockInputStream();
|
||
Block readImpl();
|
||
String getName() const { return "OneValueBlockInputStream"; }
|
||
BlockInputStreamPtr clone() { return new OneValueBlockInputStream(); }
|
||
private:
|
||
bool has_been_read;
|
||
};
|
||
|
||
|
||
/** Реализует хранилище для системной таблицы One.
|
||
* Таблица содержит единственный столбец dummy UInt8 и единственную строку со значением 0.
|
||
* Используется, если в запросе не указана таблица.
|
||
* Аналог таблицы DUAL в Oracle и MySQL.
|
||
*/
|
||
class StorageSystemOne : public IStorage
|
||
{
|
||
public:
|
||
StorageSystemOne(const std::string & name_);
|
||
|
||
std::string getName() const { return "SystemOne"; }
|
||
std::string getTableName() const { return "One"; }
|
||
|
||
const NamesAndTypesList & getColumnsList() const { return columns; }
|
||
|
||
BlockInputStreamPtr read(
|
||
const Names & column_names,
|
||
ASTPtr query,
|
||
size_t max_block_size = DEFAULT_BLOCK_SIZE);
|
||
|
||
private:
|
||
const std::string name;
|
||
NamesAndTypesList columns;
|
||
};
|
||
|
||
}
|