ClickHouse/dbms/src/Storages/System/StorageSystemClusters.h

#pragma once

#include <ext/shared_ptr_helper.hpp>
#include <Storages/IStorage.h>


namespace DB
{

class Context;

/** Implements system table 'clusters'
  *  that allows to obtain information about available clusters
  *  (which may be specified in Distributed tables).
  */
class StorageSystemClusters : private ext::shared_ptr_helper<StorageSystemClusters>, public IStorage
{
friend class ext::shared_ptr_helper<StorageSystemClusters>;

public:
    StorageSystemClusters(const std::string & name_, Context & context_);
    static StoragePtr create(const std::string & name_, Context & context_);

    std::string getName() const override { return "SystemClusters"; }
    std::string getTableName() const override { return name; }
    const NamesAndTypesList & getColumnsListImpl() const override { return columns; }

    BlockInputStreams read(
        const Names & column_names,
        const ASTPtr & query,
        const Context & context,
        QueryProcessingStage::Enum & processed_stage,
        size_t max_block_size,
        unsigned num_streams) override;

private:
    StorageSystemClusters(const std::string & name_);

private:
    const std::string name;
    NamesAndTypesList columns;
    Context & context;
};

}