Alternative for Expr (Maybe a)

[sir4ur0n]

Hello, sometimes I have several values of type Expr (Maybe a) and would like to take the first non-null value, or null if they are all null.
Intuitively I would write v1 <|> v2 but we get this error:

No instance for (GHC.Base.Alternative Expr)
        arising from a use of ‘<|>’

Fair enough.

I have found the operator <|>: but it seems to apply to tables, not to expressions 🤔

For now I have written the following:

-- | Take the first non-null value, otherwise return null.
-- This is similar to the Alternative `<|>` operator for `Maybe`, but in the `Expr` context.
orElse :: (NotNull a, DBType a) => Expr (Maybe a) -> Expr (Maybe a) -> Expr (Maybe a)
orElse ma1 ma2 = nullable ma2 nullify ma1

But it feels clunky, and I am surprised there isn't an idiomatic way to do it in Rel8.
Have I missed something?
If not, how about adding such a function/support in Rel8?