Function crash server

CREATE FUNCTION if_column_exists_normal_and_backup(tableNameToSearch TINYTEXT,

                                                   columnNameToSearch TINYTEXT)

    RETURNS BOOLEAN

    LANGUAGE SQL

BEGIN

    SET @original = tableNameToSearch;

    SET @backup = CONCAT(tableNameToSearch, '_backup');

    RETURN (

            exists(SELECT COLUMN_NAME

                   FROM INFORMATION_SCHEMA.COLUMNS

                   WHERE TABLE_NAME = @original

                     AND COLUMN_NAME = `columnnametosearch`

                )

            AND

            exists(SELECT COLUMN_NAME

                   FROM INFORMATION_SCHEMA.COLUMNS

                   WHERE TABLE_NAME = @backup

                     AND COLUMN_NAME = `columnnametosearch`

                )

        );

END