def METHOD_NAME(mapping, fields):
    """Provide support for legacy mappings which used the OID as the pk but
    default to using an autoincrementing int pk and a separate sf_id column"""
    if mapping.get_oid_as_pk():
        id_column = mapping.fields["Id"]
        fields.append(Column(id_column, Unicode(255), primary_key=True))
    else:
        fields.append(Column("id", Integer(), primary_key=True, autoincrement=True))