EntityID as Number

[smelfungus]

Hello! Thank you for that amazing framework.
Is there a way to get an underlying number (long) column expression from EntityID provided by LongIdTable?
For instance, to implement id-based shuffling with a modulo:
AnyTable.id mod shuffleSeed

[Tapac]

Do you mean SQL mod not kotlin one?

[smelfungus]

@Tapac yes! So, at the end of the day, to have the ability to write something like that:

.orderBy(
    MyTable.id mod seed to SortOrder.ASC,
    MyTable.id to SortOrder.ASC
)

[AlexeySoshin]

@dummyco
I think this should be already supported:

.orderBy(
    Expression.build { MyTable.id mod seed } to SortOrder.ASC,
    MyTable.id to SortOrder.ASC
)

[smelfungus]

@AlexeySoshin it seems like ModOp is expecting <T : Number?, S : Number?> expressions, but EntityID does not satisfy it

[AlexeySoshin]

After looking at the code some more, my comment above is incorrect, and what you need is the rem operator, not the mod operator.
As you correctly point out, ModOp executes the mod operation in the database, and that's what you want.

The reason ModOp doesn't work with EntityID is that the type is tight at the moment:

Exposed/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/Op.kt

Line 313 in 9b561b0

class ModOp<T : Number?, S : Number?>(

We could either loosen the type, which may result in runtime errors, or we may introduce another ModOp for a specific case of EntityID<Number?>

I attached a draft PR for the second case. Having difficulties testing it at the moment, though.

[smelfungus]

@AlexeySoshin, thank you for looking into it and posting a PR. The solution with separate EntityID-friendly operators and Op-s sounds good. I wonder if Exposed should have this support for all the numeric (and maybe not only numeric but any applicable) operations to a type, wrapped by EntityID. Maybe even some sort of a generic approach that would allow Exposed to unwrap the EntityID type and apply all the standard ops. Thinking out loud 😅

[Tapac]

Different mod/rem operations with EntityID columns are support since 0.41.1