module.ex

def asset_value_total_by_date_range(beginning_date, end_date \\ Date.utc_today()) do
  range = "#{Date.diff(end_date, beginning_date)} days"
  now = Date.utc_today()

  date_range_query =
    from(v in AssetValue,
      select: %{
        value: v.value,
        drange:
          fragment(
            "daterange(?, lead(?, 1) over (partition by asset_id order by ?), '[)')",
            v.value_date,
            v.value_date,
            v.value_date
          )
      }
    )

  from(v in AssetValue,
    right_join:
      day in fragment(
        "generate_series((?::date - ?::INTERVAL)::DATE, ?::date, '1 day')",
        type(^now, :date),
        type(^range, :string),
        type(^now, :date)
      ),
    join: values in subquery(date_range_query),
    on: fragment("?::date <@ drange", day),
    select: %{day: fragment("?::date", day), sum: fragment("sum(?)", values.value)},
    group_by: day,
    order_by: day
  )
  |> Repo.all()
  |> Enum.map(fn %{day: day, sum: amount} ->
    %{date: day, sum: Money.new(amount)}
  end)
end

query.sql

with values as (
	select
		value,
		daterange(value_date, lead(value_date, 1) over (partition by asset_id order by value_date), '[)') as drange
	from asset_values)
select day::date, sum(value)
from generate_series((NOW() - '45 day'::INTERVAL)::date, NOW()::date, '1 day') AS g(day)
join values on day::date <@ drange
group by day
order by day;