In Elasticsearch, you can perform a sub-field aggregation, group by, and order by using the "terms" aggregation along with the "sub-aggregation" feature. This allows you to aggregate data based on a field and then further sub-aggregate the data based on a sub-field within each bucket. You can also order the results within each bucket based on a specific criteria.

Here's an example of how to achieve sub-field aggregation, group by, and order by in Elasticsearch:

Assuming you have an index containing documents with the following structure:

json
{ "mappings": { "properties": { "category": { "type": "keyword" }, "sub_category": { "type": "keyword" }, "value": { "type": "integer" } } } }

Now, let's say you want to aggregate data based on the "category" field and then further sub-aggregate the data based on the "sub_category" field within each "category" bucket. You also want to order the sub-category buckets based on the sum of "value" in descending order.

The Elasticsearch query would look like this:

json
{ "size": 0, "aggs": { "category_agg": { "terms": { "field": "category", "size": 10 }, "aggs": { "sub_category_agg": { "terms": { "field": "sub_category", "size": 5, "order": { "total_value": "desc" } }, "aggs": { "total_value": { "sum": { "field": "value" } } } } } } } }

In this query:

  • The outer "category_agg" aggregation is a "terms" aggregation that groups the documents by the "category" field.
  • The inner "sub_category_agg" aggregation is also a "terms" aggregation that groups the documents within each "category" bucket by the "sub_category" field. The "order" parameter is used to order the sub-category buckets based on the "total_value" sub-aggregation.
  • The "total_value" sub-aggregation is a "sum" aggregation that calculates the sum of the "value" field within each "sub_category" bucket.

The result of this query will be a hierarchical aggregation structure with categories as the first level, and within each category, you will have sub-categories ordered by the sum of "value" in descending order.

Remember to adjust the "size" parameter in the aggregations to control the number of categories and sub-categories you want to include in the result. Also, ensure that the mapping of your index matches the field names used in the query.

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