Type cast issue when union null and not null value

[qwwwpp]

Version

Other

What happened?

Version 1.17.0
I am trying to list all the data in both tables with "UNION", one of the table have a NOT NULL column(created_time in the following example), and another one have a nullable column. The sqlc generated function (ListNewAndOldUsers) returns NewUser.

type NewUser struct {
	ID          int32
	CreatedTime time.Time
}

When the query returns some old_user with null created_time, it will throw unsupported Scan, storing driver.Value type <nil> into type *time.Time

Relevant log output

No response

Database schema

CREATE TABLE IF NOT EXISTS new_user(
  id int NOT NULL, 
  created_time timestamp NOT NULL
);

CREATE TABLE IF NOT EXISTS old_user(
  id int NOT NULL, 
  created_time timestamp
);

SQL queries

-- name: ListNewAndOldUsers :many
SELECT id, created_time from new_user
union
SELECT id, created_time from old_user;

Configuration

No response

Playground URL

https://play.sqlc.dev/p/e927c7567020ba8f3bdbe37538cf42a1e314d10a6a5531a4e66b4b7fb8574ce6

What operating system are you using?

macOS

What database engines are you using?

PostgreSQL

What type of code are you generating?

Go

[kyleconroy]

Thanks for the bug report. This appears to be an issue with how we generate types for unions. As the PostgreSQL docs explain here, UNION can convert different column types. In this case, it will convert the non-nullable column into nullable.

[kyleconroy]

As a workaround, you can select from the old_user table first, which uses the old_user model https://play.sqlc.dev/p/d2e7701df5fa5d4c6831b65f8aeaadb727723fcbe780bc5b49ebb08e0f1db7cf