Using elasticsearch aggregations on script_field values?

Question

I have created groovy script to calculate new field values. I then can use that script in my queries to calculate the new field value using a script_fields parameter. Here is an example:

{
    "query": {
        "filtered": {
            "query": {
                "bool": {
                    "must": {"match_all": {}}
                }
            }
        }
    },
    "script_fields":{
        "my_field":{
            "script_id":"my_field_calculator",
            "lang" : "groovy",
            "params": {}
        }
    }
}

This works just fine and I see results that each have a fields object containing my_field in it. Perfect.

Now I want to use a terms aggregation to get the counts of each occurrence of this new field value, something like this:

{
    "query": {
        "filtered": {
            "query": {
                "bool": {
                    "must": {"match_all": {}}
                }
            }
        }
    },
    "script_fields":{
        "my_field":{
            "script_id":"my_field_calculator",
            "lang" : "groovy",
            "params": {}
        }
    }
    "aggs": {
        "counts_by_my_field": {
            "terms": {
                "field": "my_field"
            }
        }
    }
}

The query runs just fine and I still see my calculated results in every field, however the aggregations object contains one key, counts_by_my_field, with an empty buckets array inside.

What am I missing? Is it possible to use script_fields in aggregations?

progrrammer · Accepted Answer · 2014-08-12 14:04:51Z

That is not possible, not yet. script_fields dont work when placed as field in aggregation or in facet.

And there is no any method to access script fields by aggregations. See explanation.

I digged into Elasticsearch implementation code,

Here is Javadoc for, ValuesSourceAggregationBuilder#script() used by Terms aggregation for scripting .

Sets the script which generates the values. If the script is configured along with the field (as in {@link #field(String)}), then * this script will be treated as a {@code value script}. A value script will be applied on the values that are extracted from * the field data (you can refer to that value in the script using the {@code _value} reserved variable). If only the script is configured * (and the no field is configured next to it), then the script will be responsible to generate the values that will be aggregated. *

This means, you cannot send "script_id" either to the aggregations. You can only do this,

POST index/type/_search
{
   "aggs": {
      "name": {
         "terms": {
            "script": "_source.data[0]",
            "lang": "groovy",
            "params": {}
         }
      }
   }
}

Hope this helps!! Thanks

coryfoo · Accepted Answer · 2014-08-13 03:24:58Z

While I have not been able to make an aggregation use a script_field value for the aggregation, I have discovered another way of accomplishing what I had hoped to do. It turns out that the aggregation will accept a script_id configuration that can calculate the script field value during aggregation.

Here is my example working with the script_id as part of the aggregation instead:

{
    "query": {
        "filtered": {
            "query": {
                "bool": {
                    "must": { "match_all": {}}
                }
            }
        }
    },
    "aggs": {
        "counts_by_my_field": {
            "terms": {
                "script_id": "my_field_calculator",
                "lang" : "groovy",
                "params": {}
            }
        }
    }
}

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