Ecto.Query.WindowAPI.first_value
You're seeing just the function
first_value
, go back to Ecto.Query.WindowAPI module for more information.
Returns value evaluated at the row that is the first row of the window frame.
from p in Post,
select: first_value(p.id) |> over(partition_by: p.category_id, order_by: p.date)
Note that this function must be invoked using window function syntax.