Ecto.Query.API.filter

You're seeing just the function filter, go back to Ecto.Query.API 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 Payment, select: filter(avg(p.value), p.value > 0 and p.value < 100)

from p in Payment, select: avg(p.value) |> filter(p.value < 0)