BUG #17202: GENERATED BY DEFAULT AS IDENTITY not inherited (but SERIAL is)

The following bug has been logged on the website:

Bug reference: 17202
Logged by: Erik Huelsmann
Email address: ehuels(at)gmail(dot)com
PostgreSQL version: 12.8
Operating system: Ubuntu Linux 20.04 (running a Docker container)
Description:

While changing the definition of a parent table from the non-standard SERIAL
column type to the SQL ANSI standard "integer GENERATED BY DEFAULT AS
IDENTITY", I'm finding a difference on the resulting columns in the child
table.

With the "SERIAL" column declaration and these table definitions:

CREATE TABLE note (id serial primary key,
note_class integer not null references note_class(id),
note text not null,
vector tsvector not null default '',
created timestamp not null default now(),
created_by text DEFAULT SESSION_USER,
ref_key integer not null,
subject text);

CREATE TABLE entity_note(
entity_id int references entity(id),
primary key(id)) INHERITS (note);

I'm getting this output for '\d':

existing=# \d note
Table "public.note"
Column | Type | Collation | Nullable |
Default
------------+-----------------------------+-----------+----------+----------------------------------
id | integer | | not null |
nextval('note_id_seq'::regclass)
note_class
| integer | | not null |
note | text | | not null |
vector | tsvector | | not null |
''::tsvector
created | timestamp without time zone | | not null | now()
created_by | text | | |
SESSION_USER
ref_key | integer | | not null |
subject | text | | |
Indexes:
"note_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
"note_note_class_fkey" FOREIGN KEY (note_class) REFERENCES
note_class(id)
Number of child tables: 6 (Use \d+ to list them.)

existing=# \d invoice_note
Table "public.invoice_note"
Column | Type | Collation | Nullable |
Default
------------+-----------------------------+-----------+----------+----------------------------------
id | integer | | not null |
nextval('note_id_seq'::regclass)
note_class | integer | | not null |
note | text | | not null |
vector | tsvector | | not null |
''::tsvector
created | timestamp without time zone | | not null | now()
created_by | text | | |
SESSION_USER
ref_key | integer | | not null |
subject | text | | |
Indexes:
"invoice_note_pkey" PRIMARY KEY, btree (id)
"invoice_note_id_idx" btree (id)
"invoice_note_vectors_idx" gist (vector)
Foreign-key constraints:
"invoice_note_ref_key_fkey" FOREIGN KEY (ref_key) REFERENCES
invoice(id)
Inherits: note

As you can see, both the "note" and "invoice_note" tables have a default
"nextval" function applied to the "id" column. When I change "SERIAL" to
"integer generated by default AS IDENTITY primary key" as demonstrated
below, the output of '\d' changes to:

REATE TABLE note (id integer generated by default AS IDENTITY primary key,
note_class integer not null references note_class(id),
note text not null,
vector tsvector not null default '',
created timestamp not null default now(),
created_by text DEFAULT SESSION_USER,
ref_key integer not null,
subject text);

CREATE TABLE invoice_note(primary key(id)) INHERITS (note);


new=# \d note
Table "public.note"
Column | Type | Collation | Nullable |
Default
------------+-----------------------------+-----------+----------+----------------------------------
id | integer | | not null | generated
by default as identity
note_class | integer | | not null |
note | text | | not null |
vector | tsvector | | not null |
''::tsvector
created | timestamp without time zone | | not null | now()
created_by | text | | |
SESSION_USER
ref_key | integer | | not null |
subject | text | | |
Indexes:
"note_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
"note_note_class_fkey" FOREIGN KEY (note_class) REFERENCES
note_class(id)
Number of child tables: 6 (Use \d+ to list them.)

new=# \d invoice_note
Table "public.invoice_note"
Column | Type | Collation | Nullable | Default

------------+-----------------------------+-----------+----------+--------------
id | integer | | not null |
note_class | integer | | not null |
note | text | | not null |
vector | tsvector | | not null |
''::tsvector
created | timestamp without time zone | | not null | now()
created_by | text | | |
SESSION_USER
ref_key | integer | | not null |
subject | text | | |
Indexes:
"invoice_note_pkey" PRIMARY KEY, btree (id)
"invoice_note_id_idx" btree (id)
"invoice_note_vectors_idx" gist (vector)
Foreign-key constraints:
"invoice_note_ref_key_fkey" FOREIGN KEY (ref_key) REFERENCES
invoice(id)
Inherits: note

Note that the "id" column of the "invoice_note" table doesn't have the
"generated by default as identity". I'm expecting the "invoice_note" table's
"id" column to have exactly the same definition as the "id" column in the
"note" table in both situations because the column isn't repeated in the
definition of the "invoice_note" definition.