What's the difference between unchanged and unset?

[saintazunya]

Hi,

I'm new to SeaORM and feels a bit confused when dealing with ActiveModel. Thank you for this amazing project.

I don't quite get the point of when should I use ActiveValue::Unchanged or ActiveValue::NotSet

I made a small experiment and the returned sql seems to be the same.

Update

assert_eq!(
        Update::one(fruit::ActiveModel {
            id: ActiveValue::set(1),
            name: ActiveValue::set("Orange".to_owned()),
            cake_id: ActiveValue::not_set(),
        })
            .build(DbBackend::Postgres)
            .to_string(),
        Update::one(fruit::ActiveModel {
            id: ActiveValue::set(1),
            name: ActiveValue::set("Orange".to_owned()),
            cake_id: ActiveValue::unchanged(Some(12345)),
        })
            .build(DbBackend::Postgres)
            .to_string(),
    );

Both queries returns
UPDATE "fruit" SET "name" = 'Orange' WHERE "fruit"."id" = 1
which means for update there is no difference in unset and unchanged

Insert

assert_eq!(
        Insert::one(fruit::ActiveModel {
            id: ActiveValue::set(1),
            name: ActiveValue::set("Orange".to_owned()),
            cake_id: ActiveValue::set(Some(12345)),
        })
            .build(DbBackend::Postgres)
            .to_string(),
        Insert::one(fruit::ActiveModel {
            id: ActiveValue::set(1),
            name: ActiveValue::set("Orange".to_owned()),
            cake_id: ActiveValue::unchanged(Some(12345)),
        })
            .build(DbBackend::Postgres)
            .to_string(),
    );

Both queries returns
INSERT INTO "fruit" ("id", "name", "cake_id") VALUES (1, 'Orange', 12345)
which means for insert there is no difference in set and unchanged.

It seems to me that unchanged is completely replaceable, and it makes me confused when to use unchanged and when to use set / unset

[billy1624]

Hey @saintazunya, welcome and thanks for the supports!

Generally speaking you don't need ActiveValue::unchanged( ... ). All you need is just set() and not_set().

For update, what you want is just update the changed / setted values. That's why the unchanged value is being ignored.

For insert, we want all setted values including those unchanged values to be inserted into db.

That's the behaviour for update & insert :)