class RowExcIgnore(Code):

    def __init__(self, row_type, select_query, with_row, cols=None,

        exc='unique_violation'):

        Code.__init__(self, lang='plpgsql')

        select_query = as_Code(select_query)

        with_row = as_Code(with_row)

        self.row_type = row_type

        self.select_query = select_query

        self.with_row = with_row

        self.cols = cols

        self.exc = exc

    def to_str(self, db):

        if self.cols == None: row_vars = [Table('row')]

        else: row_vars = [Col(c.name, 'row') for c in self.cols]

        str_ = '''\

DECLARE

    row '''+self.row_type+''';

BEGIN

    /* Need an EXCEPTION block for each individual row because "When an error is

    caught by an EXCEPTION clause, [...] all changes to persistent database

    state within the block are rolled back."

    This is unfortunate because "A block containing an EXCEPTION clause is

    significantly more expensive to enter and exit than a block without one."

    (http://www.postgresql.org/docs/8.3/static/plpgsql-control-structures.html\

#PLPGSQL-ERROR-TRAPPING)

    */

    FOR '''+(', '.join((v.to_str(db) for v in row_vars)))+''' IN

'''+self.select_query.to_str(db)+'''

    LOOP

        BEGIN

            RETURN QUERY

'''+self.with_row.to_str(db)+'''

;

        EXCEPTION

            WHEN '''+self.exc+''' THEN NULL; -- continue to next row

        END;

    END LOOP;

END;\

'''

        return str_