type/2 in select is great.
One use case came up that is still a bit awkward: converting a sum(x) into a Money.Ecto.Type:
The workaround I found was to wrap it in a subquery:
from account_balance in subquery(
from t in Transaction,
group_by: [t.account_id],
select: %{account_id: t.account_id, balance: sum(t.amount)})
select %{account_id: account_balance.account_id, balance: type(account_balance.balance, Money.Ecto.Type)}
If the subquery layer could be removed it would be amazing!
I build some utterly massive queries to get information from an old Oracle database. If I were to return everything then it would be beyond huge (it has hundreds of columns in some cases), so I return data massaged into a better format (getting some information like ethnicity involves querying 5 tables, or 6 depending on the detail wanted), however some information is only available depending on what was passed in, and the sheer combination of options that can be passed in would be thousands large if I were to make a custom query for each combination of input and return information, so instead I’ve been building information to generate a select as it ramps down the whole line of things, changing it from thousands of total combinations to the 9 or so from the inputs and just branch based on their combinations for specific shared outputs. This means that I can reduce it to a linear set of code instead of my prior N*M combinations, thus making it substantially easier to read and follow.
I’ve not rewritten any of the older ones yet, they are a bit of a many-many-screen horrors each, but sometime… >.>
(I don’t want to break them, they are brittle, this will reduce a lot of the brittleness though once I do it.)
Thanks @josevalim, #2163 opened.
Related, but slightly different is when a schema declares a virtual field that is populated in a query:
schema "accounts" do
field :name, :string
field :balance, Money.Ecto.Type, virtual: true
has_many :transactions, Transaction
timestamps()
end
accounts_with_balance = Repo.all(from a in Account, select: %{a | balance: 123})
The current behaviour doesn’t load the value through the declared custom type.
Would you be open to automatically casting the virtual field to the type declared in the schema?
