/// visible for UTs
    static ASTPtr make_partition_expression(const DB::Names & partition_columns)
    {
        /// Parse the following expression into ASTs
        /// cancat('/col_name=', 'toString(col_name)')
        bool add_slash = false;
        ASTs arguments;
        for (const auto & column : partition_columns)
        {
            // partition_column=
            std::string key = add_slash ? fmt::format("/{}=", column) : fmt::format("{}=", column);
            add_slash = true;
            arguments.emplace_back(std::make_shared<DB::ASTLiteral>(key));

            // ifNull(toString(partition_column), DEFAULT_PARTITION_NAME)
            // FIXME if toString(partition_column) is empty
            auto column_ast = std::make_shared<DB::ASTIdentifier>(column);
            ASTs if_null_args{makeASTFunction("toString", ASTs{column_ast}), std::make_shared<DB::ASTLiteral>(DEFAULT_PARTITION_NAME)};
            arguments.emplace_back(makeASTFunction("ifNull", std::move(if_null_args)));
        }
        return DB::makeASTFunction("concat", std::move(arguments));
    }