Inconsistency in cvterm table when setting dbxref_id on delete set null

[dreyes17]

Hello,

here is the table cvterm. The column dbxref_id couldn't be null nut the foreign key is set to on delete set null. I have checked other tables with dbxref_id and they can be null such as the table feature for example. But in this case I think that having a cvterm without knowing its provenance doesn't make sense. Do you agree? So for me it should be on delete cascade rather than making dbxref_id nullable.

create table cvterm ( cvterm_id bigserial not null, primary key (cvterm_id), cv_id bigint not null, foreign key (cv_id) references cv (cv_id) on delete cascade INITIALLY DEFERRED, name varchar(1024) not null, definition text, dbxref_id bigint not null, foreign key (dbxref_id) references dbxref (dbxref_id) on delete set null INITIALLY DEFERRED, is_obsolete int not null default 0, is_relationshiptype int not null default 0, constraint cvterm_c1 unique (name,cv_id,is_obsolete), constraint cvterm_c2 unique (dbxref_id) );

There are also some tables where you explicitly put null even if it is initialized to that value by default so I don't know if you are missing the not or not. For instance:

create table featuremap ( featuremap_id bigserial not null, primary key (featuremap_id), name varchar(255), description text, unittype_id bigint null, foreign key (unittype_id) references cvterm (cvterm_id) on delete set null INITIALLY DEFERRED, constraint featuremap_c1 unique (name) );

Maybe you can give an overview to the nulls.

Thank you