Elasticsearch aggregations with object type fields

Question

I am trying to figure something out :

Here's an example of a document that contains object properties, and then trying to do simple terms aggregations. https://gist.github.com/BAmine/80e1be219d2ac272561a

{
  "took": 2,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "failed": 0
},
  "hits": {
    "total": 1,
    "max_score": 0,
    "hits": []
  },
"aggregations": {
   "test": {
      "buckets": [
         {
            "key": "canine",
            "doc_count": 1,
            "test2": {
               "buckets": [
                  {
                     "key": "cat",
                     "doc_count": 1
                  },
                  {
                     "key": "dog",
                     "doc_count": 1
                  },
                  {
                     "key": "tiger",
                     "doc_count": 1
                  },
                  {
                     "key": "wolf",
                     "doc_count": 1
                  }
               ]
            }
         },
         {
            "key": "feline",
            "doc_count": 1,
            "test2": {
               "buckets": [
                  {
                     "key": "cat",
                     "doc_count": 1
                  },
                  {
                     "key": "dog",
                     "doc_count": 1
                  },
                  {
                     "key": "tiger",
                     "doc_count": 1
                  },
                  {
                     "key": "wolf",
                     "doc_count": 1
                  }
               ]
            }
         }
      ]
   }
}

}

The question is : How can I avoid getting, in my sub-aggregations, buckets whose keys do not belong to the parent aggregation's keys ( example : cat and tiger are not in the property whose label is canine) ? Is there a way to do this without using nested properties ?

Thank you !

kiml42 · Accepted Answer · 2015-12-10 13:22:50Z

To have this work with the data as is; you could set the animals field's type to nested:

"animals":{
    "type": "nested",
    "properties": {
        "label" : { "type" : "string"},
        "names":{
          "properties":{
            "label" : {"type" : "string"}
          }
        }
    }

This allows you to make requests of that part of the document as separate objects. You could then use two filter aggregations within nested aggregations, one filtering for label == feline and the other for label == canine, you could then use aggregations within these that would give you the two separate lists.

This solution would have the drawback of having to add another nested filter aggregation for each new class of animals you add later.

the solution @vadik suggested seems superior to me, as there doesn't seem to be anything about these lists that requires them to be in the same document. If there is, you could make them be in separate documents with a common parent.

vaidik · Accepted Answer · 2014-07-19 00:27:41Z

The problem is that you have one document for both the animals. And that's why you will get all the four animals. I suggest another approach instead. Create 2 documents, 1 each for every item in the animals array.

And try on similar lines and you will get your result.

Why are you not getting the result? Aggregations framework gets the only document, and finds the occurrences of animals.label. It finds two, canine and feline and it outputs both. Further, there is another aggregation within the previous aggregation that wants to aggregate the key animals.names.label. Now there is just one document, which has both the keys of type animals.label and then for each key, the document has all the four values for key animals.names.label. So ES is right. The problem is that the item in animals must be independently identifiable as a document. And then aggs framework will be able to consider it as a container and your intention to aggregate animals.names.label inside animals.label. This is exactly what will happen when you will split the document into two documents.

Another thing that you can try is working with Nested Types. To understand why nested types may help, read this article.

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