@kip You might know if this is possible or not.

I have been experimenting with different ways of updating a balance field in the database that is of the usual Money type.

Consider this:

    Multi.update_all(
      multi,
      :wallet,
      fn _ ->
        from(w in Wallet,
          where: w.id == ^wallet_id,
          update: [inc: [balance: type(^amount, ^Money.Ecto.Composite.Type.cast_type())]]
        )
      end,
      []
    )

This results in an error:

     ** (Postgrex.Error) ERROR 42883 (undefined_function) operator does not exist: money_with_currency + money_with_currency
     
         query: UPDATE "wallets" AS w0 SET "balance" = w0."balance" + $1::money_with_currency WHERE (w0."id" = $2)
     
         hint: No operator matches the given name and argument types. You might need to add explicit type casts.

I have run the “aggregate functions for money” migration although I didn’t think it would help since this is +, not sum.

I think maybe this kind of syntax just isn’t possible? Can anyone confirm?