Is it possible to create a date histogram from the output of a date histogram?

[crickes (Steve Crickett)]

I am trying to create some statistical output based on event data. I have script that will search and count events over a period of time and creates a date histogram, with the bucket size being configurable. the output of which looks like this:

"aggregations": {
"per_second_histo": {
  "buckets": [
    {
      "key_as_string": "2017-02-14T00:00:00.000Z",
      "key": 1487030400000,
      "doc_count": 0
    },
    {
      "key_as_string": "2017-02-14T00:00:01.000Z",
      "key": 1487030401000,
      "doc_count": 0
    },
    {
      "key_as_string": "2017-02-14T00:00:02.000Z",
      "key": 1487030402000,
      "doc_count": 0
    },
    {
      "key_as_string": "2017-02-14T00:00:03.000Z",
      "key": 1487030403000,
      "doc_count": 0
    },
    {
      "key_as_string": "2017-02-14T00:00:04.000Z",
      "key": 1487030404000,
      "doc_count": 0
    },

What I want to do now is create a second date histogram, with buckets of 5 minute periods containing stats for that period using a stats bucket, but i'm struggling with how to point the stats bucket at a selection of the previous date histogram. I've seen it github that something called a bucket reducer was proposed, and the ticket was closed with the introduction of pipeline aggregations, but I can't figure out how to do it. Can anyone shed some advice on this please?