Delete datapoint with same value

Im saving the data from my gas meter to a database. Every 30mins im getting the current meter reading.

When there is no change i only want to keep the first entry

for example:
#1 1:00 8738m²
#2 1:30 8740m²
#3 2:00 8740m²
#4 2:30 8740m²
#5 3:00 8744m²

in this case i want to use a task job but i dont want to keep #3 and #4.
how can i do this?

I found this as a suggestion from another user

from(bucket: "sensors")
  # Usual range and filter.
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> filter(fn: (r) => r._field == "temp")

  # Copy "_value" column so that the original won't get lost.
  |> duplicate(column: "_value", as: "diff")

  # Convert "diff"-column to the difference from pervious row.
  |> difference(
    columns: ["diff"],
    keepFirst: true  # Stores null in first "diff"-column.

  # Keep the first null-valued row; it is the initial value,
  # and all other rows with a change (diff != 0).
  |> filter(fn: (r) => not exists r.diff or r.diff != 0)