Aggregation on terms and intervals in elasticsearch

My documents are like this below:

{
    "uri" : "post:1130a8ef197882bc3ebd",
    "topic_list" : [
        "bye",
        "hello"
    ],
    "datetime" : "2010-06-06T22:08:49"
}

I want to make a query to aggregate on both datetime and topic_list. My desired output is to tell me that on each time interval, how many docs has the hello topic in topic_list.

What I’ve tried was this:

{
  "size": 0, 
  "aggs": {
    "test": {
      "terms": {
        "field": "topic_list"
        
      }
    }
  }
}

But the output just tell me how many docs containing every topic at all times and not in the intervals.
How can I create such aggregation?

>Solution :

You need to add two more things:

1. a query to only restrict the results to documents containing the topic "hello". If you’re only interested in the document count per time interval, you don’t need the terms aggregation on the topic_list field
2. a date_histogram aggregation to create time intervals

Here is the query:

{
  "size": 0,
  "query": {
    "term": {
      "topic_list": "hello"
    }
  },
  "aggs": {
    "intervals": {
      "date_histogram": {
        "field": "date",
        "calendar_interval": "1d"
      }
    }
  }
}