'change index on partner_id to a multi-column index on (partner_id, ref), the new index will behave in the
same way when we search on partner_id, with the addition of being optimal when having a query that will
search on partner_id and ref at the same time (which is the case when we open the bank reconciliation widget)'

@api.model_cr
def init(self):

    cr = self._cr
    cr.execute('DROP    INDEX    IF    EXISTS    account_move_line_partner_id_index')
    cr.execute('SELECT    indexname    FROM    pg_indexes    WHERE    indexname    =    %s', ('account_move_line_partner_id_ref_idx',))
    if (not cr.fetchone()):
        cr.execute('CREATE    INDEX    account_move_line_partner_id_ref_idx    ON    account_move_line    (partner_id,    ref)')
