DbException.__init__(self, 'for name: '+str(name), cause)

        self.name = name

class ExceptionWithColumns(DbException):

    def __init__(self, cols, cause=None):

        DbException.__init__(self, 'for columns: '+(', '.join(cols)), cause)

class NullValueException(ExceptionWithColumns): pass

class DuplicateTableException(ExceptionWithName): pass

    except Exception, e:

        if not recover: raise # need savepoint to run index_cols()

        msg = str(e)

        match = re.search(r'duplicate key value violates unique constraint '

            r'"((_?[^\W_]+)_[^"]+)"', msg)

        if match:

            try: cols = index_cols(db, table, constraint)

            except NotImplementedError: raise e

            else: raise DuplicateKeyException(cols, e)

        match = re.search(r'null value in column "(\w+)" violates not-null '

            r'constraint', msg)

        if match: raise NullValueException([match.group(1)], e)

            r'CONTEXT:.*\bfunction "(\w+)".*\bat assignment', msg)

        match = re.search(r'relation "(\w+)" already exists', msg)

        if match: raise DuplicateTableException(match.group(1), e)

        match = re.search(r'function "(\w+)" already exists', msg)

        if match: raise DuplicateFunctionException(match.group(1), e)

        raise # no specific exception raised

##### Basic queries