ClickHouse/dbms/include/DB/Storages/System/StorageSystemColumns.h

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#pragma once
#include <ext/shared_ptr_helper.hpp>
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#include <DB/Storages/IStorage.h>
#include <DB/Interpreters/Context.h>
namespace DB
{
/** Реализует системную таблицу columns, которая позволяет получить информацию
* о столбцах каждой таблицы для всех баз данных.
*/
class StorageSystemColumns : private ext::shared_ptr_helper<StorageSystemColumns>, public IStorage
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{
friend class ext::shared_ptr_helper<StorageSystemColumns>;
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public:
static StoragePtr create(const std::string & name_);
std::string getName() const override { return "SystemColumns"; }
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,
size_t max_block_size = DEFAULT_BLOCK_SIZE,
unsigned threads = 1) override;
private:
StorageSystemColumns(const std::string & name_);
private:
const std::string name;
NamesAndTypesList columns;
};
}