Re: Can't find not null constraint, but \d+ shows that

jian he <jian.universality@gmail.com> 于2024年4月10日周三 14:10写道：

> On Wed, Apr 10, 2024 at 1:29 AM Alvaro Herrera <alvherre@alvh.no-ip.org>
> wrote:
> >
> > On 2024-Mar-29, Tender Wang wrote:
> >
> > > I think aboved case can explain what's meaning about comments in
> > > dropconstraint_internal.
> > > But here, in RemoveConstraintById() , we only care about primary key
> case,
> > > so NOT NULL is better to removed from comments.
> >
> > Actually, I think it's better if all the resets of attnotnull occur in
> > RemoveConstraintById, for both types of constraints; we would keep that
> > block in dropconstraint_internal only to raise errors in the cases where
> > the constraint is protecting a replica identity or a generated column.
> > Something like the attached, perhaps, may need more polish.
> >
>
> DROP TABLE if exists notnull_tbl2;
> CREATE TABLE notnull_tbl2 (c0 int generated by default as IDENTITY, c1
> int);
> ALTER TABLE notnull_tbl2 ADD CONSTRAINT Q PRIMARY KEY(c0, c1);
> ALTER TABLE notnull_tbl2 DROP CONSTRAINT notnull_tbl2_c0_not_null;
> ALTER TABLE notnull_tbl2 DROP c1;
> \d notnull_tbl2
>
> last "\d notnull_tbl2" command, master output is:
>                         Table "public.notnull_tbl2"
>  Column |  Type   | Collation | Nullable |             Default
>
> --------+---------+-----------+----------+----------------------------------
>  c0     | integer |           | not null | generated by default as identity
>
>
>
> last "\d notnull_tbl2" command, applying
> 0001-Correctly-reset-attnotnull-when-constraints-dropped-.patch
> output:
>                         Table "public.notnull_tbl2"
>  Column |  Type   | Collation | Nullable |             Default
>
> --------+---------+-----------+----------+----------------------------------
>  c0     | integer |           |          | generated by default as identity
>

Hmm,
ALTER TABLE notnull_tbl2 DROP c1; will not call dropconstraint_internal().
When dropping PK constraint indirectly, c0's attnotnull was set to false in
RemoveConstraintById().


-- 
Tender Wang
OpenPie:  https://en.openpie.com/