arcsize =
    from(bucket: "metrics")
        |> range(start: -duration(v: task.every))
        |> filter(fn: (r) => r._measurement == "zfs" and r._field == "arcstats_size")
        |> mean()

used =
    from(bucket: "metrics")
        |> range(start: -duration(v: task.every))
        |> filter(fn: (r) => r._measurement == "mem" and r._field == "used")
        |> mean()

free =
    from(bucket: "metrics")
        |> range(start: -duration(v: task.every))
        |> filter(fn: (r) => r._measurement == "mem" and r._field == "available")
        |> mean()

union(tables: [arcsize, used, free])
    |> group()
    |> map(
        fn: (r) =>
            ({r with used: r.used - r.arcstats_size,
                available: r.available + r.arcstats_size,
                _time: r._start,
            }),
    )
    |> group(columns: ["_time", "host"])
    |> to(bucket: "metrics-preprocessed")