How Elasticsearch do filter aggregation

Question

I need to do average aggregation, but I want to filter some values. In the below examples, I want filter the length=100, so I want to do average for length (with doc #1 and doc #2) and for width with all documents. So I expect to see length average as 9 and width average as 5. What should I do?

document example:

["id": 1, "length": 10, "width":8]
["id": 2, "length": 8, "width":2]
["id": 3, "length": 100, "width":5]

And In some other case, length may not exist, How about this case?

["id": 1, "length": 10, "width":8]
["id": 2, "length": 8, "width":2]
["id": 3, "width":5]

termAggregation.subAggregation(AggregationBuilders.avg("length").field("length"))
.subAggregation(AggregationBuilders.avg("width").field("width"));

Answer 1

Your aggregation query will look like below for excluding 100 from aggregation. You need to use filter aggregation and inside that avg as sub aggregation.

{
  "size": 0,
  "aggs": {
    "cal": {
      "filter": {
        "bool": {
          "must_not": [
            {
              "match": {
                "length": "100"
              }
            }
          ]
        }
      },
      "aggs": {
        "avg_length": {
          "avg": {
            "field": "length"
          }
        }
      }
    },
    "avg_width":{
      "avg": {
        "field": "width"
      }
    }
  }
}

Java code

AvgAggregationBuilder widthAgg = new AvgAggregationBuilder("avg_width").field("width");
        AvgAggregationBuilder lengthAgg = new AvgAggregationBuilder("avg_length").field("length");

        FilterAggregationBuilder filter = new FilterAggregationBuilder("cal",
                QueryBuilders.boolQuery().mustNot(QueryBuilders.matchQuery("length", "100")));
        filter.subAggregation(lengthAgg);
        
        SearchSourceBuilder ssb = new SearchSourceBuilder();
        ssb.aggregation(filter);
        ssb.aggregation(widthAgg);
        
        System.out.println(ssb.toString());

Response

"aggregations": {
    "avg_width": {
      "value": 5
    },
    "cal": {
      "meta": {},
      "doc_count": 3,
      "avg_length": {
        "value": 9
      }
    }
  }