Re: ALTER COLUMN ... SET EXPRESSION to alter stored generated column's expression - Mailing list pgsql-hackers

On Fri, Oct 6, 2023 at 6:06 PM Peter Eisentraut <peter@eisentraut.org> wrote:
>
> On 28.08.23 11:54, Amul Sul wrote:
> > Thanks for the review comments, I have fixed those in the attached
> > version. In
> > addition to that, extended syntax to have the STORE keyword as suggested by
> > Vik.
>
> An additional comment: When you change the generation expression, you
> need to run ON UPDATE triggers on all rows, if there are any triggers
> defined.  That is because someone could have triggers defined on the
> column to either check for valid values or propagate values somewhere
> else, and if the expression changes, that is kind of like an UPDATE.
>
> Similarly, I think we should consider how logical decoding should handle
> this operation.  I'd imagine it should generate UPDATE events on all
> rows.  A test case in test_decoding would be useful.
>

Should we treat it the same fashion as ALTER COLUMN ... TYPE which
rewrites the column values? Of course that rewrites the whole table,
but logically they are comparable.

--
Best Wishes,
Ashutosh Bapat