ClickHouse/src/TableFunctions/TableFunctionNull.h

#pragma once

#include <Core/Types.h>
#include <DataTypes/DataTypesNumber.h>
#include <TableFunctions/ITableFunction.h>


namespace DB
{

/* null(structure) - creates a temporary null storage
 *
 * Used for testing purposes, for convenience writing tests and demos.
 */
class TableFunctionNull : public ITableFunction
{
public:
    static constexpr auto name = "null";
    std::string getName() const override { return name; }

    bool needStructureHint() const override { return structure == "auto"; }

    void setStructureHint(const ColumnsDescription & structure_hint_) override { structure_hint = structure_hint_; }

private:
    StoragePtr executeImpl(const ASTPtr & ast_function, ContextPtr context, const String & table_name, ColumnsDescription cached_columns) const override;
    const char * getStorageTypeName() const override { return "Null"; }

    void parseArguments(const ASTPtr & ast_function, ContextPtr context) override;
    ColumnsDescription getActualTableStructure(ContextPtr context) const override;

    String structure = "auto";
    ColumnsDescription structure_hint;

    const ColumnsDescription default_structure{NamesAndTypesList{{"dummy", std::make_shared<DataTypeUInt8>()}}};
};
}