Doing a bulk insert with missing=default uses the default value of the domain instead of the column

[laurenceisla]

Environment

• PostgreSQL version: 15.7
• PostgREST version: 12.2.3
• Operating system: NixOS

Description of issue

As the title says. According to the PostgreSQL docs:

The default expression will be used in any insert operation that does not specify a value for the column. If a default value is defined for a particular column, it overrides any default associated with the domain. In turn, the domain default overrides any default value associated with the underlying data type.

To reproduce this:

create domain defdom as integer default 1;

create table test_defdom (
  id int primary key,
  val api.defdom default 10
);

curl -X POST 'localhost:3000/test_defdom?columns=id,val' \
  -H 'Content-Type: application/json' \
  -H 'Prefer: missing=default, return=representation' \
  -d '[{"id": 1}]'

Expected:

[{"id":1,"val":10}]

Got:

[{"id":1,"val":1}]

Solution

Check if the defaults of the columns are not null first, otherwise use the domain default instead.

postgrest/src/PostgREST/SchemaCache.hs

Lines 624 to 629 in f21053d

	CASE
	WHEN t.typbasetype != 0 THEN pg_get_expr(t.typdefaultbin, 0)
	WHEN a.attidentity = 'd' THEN format('nextval(%L)', seq.objid::regclass)
	WHEN a.attgenerated = 's' THEN null
	ELSE pg_get_expr(ad.adbin, ad.adrelid)::text
	END AS column_default,