Update Date Histogram Agg

[panda01]

Closes #3482.

[Agg/DateHistogram] Changed the date histogram Aggregation to use time_zone instead of pre_zone.

[spalger]

This works for intervals smaller than 1 day, but doesn't work for large intervals.

[spalger]

Reached out to @cbuescher for his opinion on the matter

[cbuescher]

Tried this for week interval on current master. Not 100% sure what your expectations are here, but this is how it should work now:

• time_zone shifts bucket boundaries to start/stop in the specified time_zone
• in the returned bucket:
  • key is now always millis in UTC. I think this changed, using only "pre_zone" you were able to get buckets in local time, but this was one of the things we wanted to remove
  • key_as_string returns a formated version of that key in the specified timezone, e.g. for "time_zone": "-02:00"

"key_as_string": "2014-05-26T00:00:00.000-02:00",

• you can specify a different format like e.g. format": "yyyy-MM-dd/HH:mm.ss#z would give you "2014-06-30/00:00.00#-02:00"

If you need the bucket date in local time, you should be able to either use the key_as_string or you have to do the math using the UTC key.

When I do this on some random dates on master I get:

GET /dates/docs/_search
{
  "query": { "match_all": {}}, 
    "aggs" : {
        "articles_over_time" : {
            "date_histogram" : {
                "field" : "date",
                "interval" : "week",
                "min_doc_count" : 0,
                "time_zone": "-02:00",
                "format": "yyyy-MM-dd/HH:mm.ss#z"
            }
        }
    }  
}

Returns:
"aggregations": {
      "articles_over_time": {
         "buckets": [
            {
               "key_as_string": "2014-05-26/00:00.00#-02:00",
               "key": 1401069600000,
               "doc_count": 1
            },
            {
               "key_as_string": "2014-06-02/00:00.00#-02:00",
               "key": 1401674400000,
               "doc_count": 0
            },
            {
               "key_as_string": "2014-06-09/00:00.00#-02:00",
               "key": 1402279200000,
               "doc_count": 0
            }
[...]
}

So the first bucket key is UTC 2014-05-26T02:00:00 but the key_as_string formats this in local time in the specified time zone.

Hope this helps, let me know if you need more info.

[panda01]

That is incredibly helpful, Thanks!

[spalger]

Thanks for taking a look @cbuescher. Looks like it's just a disparity between 1.4.4 and master.

We won't be able to merge this until we bump the minimum elasticsearch version.

[rashidkpc]

Closing in favor of #4301