Add composite index to position : drive_id + date instead of drive_id

[IlyaDiallo]

This is a proposed fix to the #2278 issue. On my setup with 5 million records in the position table, the close_drive function executes in under 7 seconds from 55 seconds before the index change.
An (untested) alternative fix would be to change the queries in the close_drive function like this:

    filtered_positions =
      from p in Position,
        where:
          p.drive_id == ^id and
            not is_nil(p.ideal_battery_range_km) and
            not is_nil(p.odometer)

    non_streamed_drive_data =
      from p in subquery(filtered_positions),
        select: %{
          start_ideal_range_km: first_value(p.ideal_battery_range_km) |> over(:w),
          end_ideal_range_km: last_value(p.ideal_battery_range_km) |> over(:w),
          start_rated_range_km: first_value(p.rated_battery_range_km) |> over(:w),
          end_rated_range_km: last_value(p.rated_battery_range_km) |> over(:w)
        },
        windows: [
          w: [
            order_by:
              fragment("? RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING", p.date)
          ]
        ],
        limit: 1

The idea here is to pre-filter to work with a subset of the positions table (drive_id = id) instead of the whole table.

[adriankumpf]

Good catch! Thanks.