Re: BUG #17056: Segmentation fault on altering the type of the foreign table column with a default

On 6/10/21 6:10 PM, Tom Lane wrote:
> PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
>> CREATE FOREIGN DATA WRAPPER dummy;
>> CREATE SERVER s0 FOREIGN DATA WRAPPER dummy;
>> CREATE FOREIGN TABLE ft1 (c1 integer NOT NULL) SERVER s0;
>> ALTER FOREIGN TABLE ft1 ADD COLUMN c8 integer DEFAULT 0;
>> ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE char(10);
> Hmm. The equivalent DDL on a plain table works fine, but this is
> crashing in the code that manipulates attmissingval. I suspect some
> confusion about whether a foreign table column should even *have*
> attmissingval. Andrew, any thoughts?
>
>

My initial thought would be that it should not. If the foreign table has
rows with missing columns then it should be up to the foreign server to
supply them transparently. We have no notion what the foreign semantics
of missing columns are.

I can take a look at a fix tomorrow. My inclination would be simply to
skip setting attmissingval for foreign tables.

cheers

andrew

--
Andrew Dunstan
EDB: https://www.enterprisedb.com