Ecto.Query.WindowAPI.filter

You're seeing just the function filter, go back to Ecto.Query.WindowAPI module for more information.

Applies the given expression as a FILTER clause against an aggregate. This is currently only supported by Postgres.

from p in Post,
     select: avg(p.value)
             |> filter(p.value > 0 and p.value < 100)
             |> over(partition_by: p.category_id, order_by: p.date)