Re: +(pg_lsn, int8) and -(pg_lsn, int8) operators

On Thu, Apr 30, 2020 at 11:40:59PM +0900, Fujii Masao wrote:
> Also the number of bytes can be added into and substracted from LSN using the
> <literal>+(pg_lsn,numeric)</literal> and <literal>-(pg_lsn,numeric)</literal>
> operators, respectively. Note that the calculated LSN should be in the range
> of <type>pg_lsn</type> type, i.e., between <literal>0/0</literal> and
> <literal>FFFFFFFF/FFFFFFFF</literal>.
> -----------------

That reads fine.

>> + /* XXX would it be better to return NULL? */
>> + if (NUMERIC_IS_NAN(num))
>> + ereport(ERROR,
>> + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
>> + errmsg("cannot convert NaN to pg_lsn")));
>> That would be good to test, and an error sounds fine to me.
>
> You mean that we should add the test that goes through this code block,
> into the regression test?

Yes, that looks worth making sure to track, especially if the behavior
of this code changes in the future.
--
Michael