How to extract month from datetime in Kibana and Elastisearch?

I put some data into Elasticsearch to visualize it in Kibana. My goal is to maximally avoid Scripted fields in Kibana, because they are computationally expensive.

I want to make a chart showing months in the X axis and count in Y axis. For this I need to format EventDate into month. What is the best way to do it?

This is my PUT statement:

PUT /test
{
    "mappings": {
      "registry": {
      "_source": {
        "enabled": true
      },
      "_all": {
        "enabled": true
      },
        "properties": {
          "Id": {
            "type":"text"
          },
          "Location": {
            "type":"geo_point"
          },
          "Country": {
            "type":"keyword"
          },
          "EventDate": {
            "type":"date",
            "format": "yyyy-MM-dd HH:mm:ss.SSS"
          },
        }
      }
    }
}

Solution

I don't know the exact usecase, but you can use Histogram aggregation or regex queries which match the month in EventDate.

Here is the docu of the DateHistogramm Aggregation: https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-datehistogram-aggregation.html