Re: BUG #16818: progress reporting ALTER TABLE ADD UNIQUE

Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> On 2021-Jan-11, PG Bug reporting form wrote:
>> The progress reprorting for `ALTER TABLE test ADD UNIQUE (col)` is in
>> `pg_stat_progress_create_index`. As it indeed creates an index, that is not
>> too unexpected, but the `command` column of that view reports `CREATE
>> INDEX`, and _that_ is somewhat unexpected. A reasonable expectation would be
>> `ALTER TABLE ADD CONSTRAINT` or comparable.

> Hmm, seems a reasonable complaint.  Are there other command wordings
> that would need to be handled?  I can't think of any (but I already
> overlooked this one, evidently ...)

TBH, I think that reporting it as "CREATE INDEX" is good, and what
the OP is asking for is less good.  Creating an index is what is
actually the time-consuming step here --- making the catalog entries
for the constraint is negligible.  Also, just how picky would we be
about replicating the command spelling -- e.g., consider "ALTER TABLE t
ADD PRIMARY KEY(p)" vs "ALTER TABLE t ADD CONSTRAINT c PRIMARY KEY(p)"
vs "ALTER TABLE t ADD COLUMN c int PRIMARY KEY" vs all the same options
for UNIQUE vs all the same options for EXCLUSION vs yadda yadda.
That is not going to be helpful to anybody, IMO, especially not
automated tools that might be watching the progress view.

It's reasonable for the view to distinguish REINDEX and CONCURRENTLY
options, as those are relevant to performance, but I don't think we
should add purely-cosmetic variations.

            regards, tom lane