Provision to add condition to remove bucket in aggregation

[Vineeth-Mohan]

In bucket aggregation , its a common use case to invalidate or rather remove some of the buckets based on some conditions.
Sample use cases are

1. For term aggregation bucket nested with stats aggregation , remove all buckets with same stats min and stats max as same.
2. Terms aggregation nested over stats - Remove all buckets having average less than 10

So basically as we do sorting based on path conditions , we should also be able to drop buckets.
Eg:

{
    "aggs" : {
        "countries" : {
            "terms" : {
                "field" : "address.country",
                "drop" : { "condition" : "females.height_stats.avg > 10 "  }
            },
            "aggs" : {
                "females" : {
                    "filter" : { "term" : { "gender" : { "female" }}},
                    "aggs" : {
                        "height_stats" : { "stats" : { "field" : "height" }}
                    }
                }
            }
        }
    }
}

The above aggregation will drop all country whose average female height is more than 10.

[clintongormley]

Hi @Vineeth-Mohan

We're planning on supporting bucket filtering with #8110, eg :

{
  "aggs": {
    "countries": {
      "terms": {
        "field": "address.country"
      },
      "having": {
        "script": "_bucket.female.height_stats.avg > min_height",
        "params": {
          "min_height": 10
        }
      },
      "aggs": {
        "females": {
          "filter": {
            "term": {
              "gender": "female"
            }
          },
          "aggs": {
            "height_stats": {
              "stats": {
                "field": "height"
              }
            }
          }
        }
      }
    }
  }
}

Or, for an example that refers to two separate aggregations, eg only include countries where the average female height is greater than the average height overall:

{
  "aggs": {
    "female_avg_height_above_overall_agv": {
      "trim": {
        "buckets": "address.country",
        "script": "_bucket.female.avg_height.value > avg_height.value"
      }
    },
    "avg_height": {
      "avg": {
        "field": "height"
      }
    },
    "countries": {
      "terms": {
        "field": "address.country"
      },
      "aggs": {
        "female": {
          "terms": {
            "term": {
              "gender": "female"
            }
          },
          "aggs": {
            "avg_height": {
              "avg": {
                "field": "height"
              }
            }
          }
        }
      }
    }
  }
}