Can not remove hits.hits.sort field from response of /_search request with sort

[muziyoshiz (Masahiro Yoshizawa)]

Hello Elasticsearch Team,

In our use case, we want to get only document IDs of the matched documents as a result of search API /_search.

But when I call search API with a query including "sort" field, the response contains unnecessary hits.hits.sort field as follows.

{
  "took": 6,
  "timed_out": false,
  "_shards": {
    "total": 6,
    "successful": 6,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": {
      "value": 1,
      "relation": "eq"
    },
    "max_score": null,
    "hits": [
      {
        "_index": "example1",
        "_type": "_doc",
        "_id": "12345",
        "_score": null,
        "sort": [
          "Unnecessary keyword value",
          "12345"
        ]
      }
    ]
  }
}

"_source":false was ignored for the hits.hits.sort field.
In our use case, the keyword field for sort may contain long keyword. So it consumes Java heap space uselessly.

Can I remove hits.hits.sort field itself or the keyword text in the field by any option?

Thanks.

[dadoonet (David Pilato)]

Welcome! I don't think you can. That being said I don't think that displaying 10 sort values is the problem.

You should read https://www.elastic.co/guide/en/elasticsearch/reference/current/search-request-body.html#_memory_considerations

It says that you are loading in memory all the sort values. Even though you are displaying only 10 afterwards.

May be using index sorting could help? See https://www.elastic.co/guide/en/elasticsearch/reference/current/index-modules-index-sorting.html

[muziyoshiz (Masahiro Yoshizawa)]

Thank you very much!

Sorry for my incomplete explanation. we used bigger size than default value (10).
So the size of the response came to an issue.

After my post, I found filter_path parameter. It may be the solution for what we wanted to do.
https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#common-options-response-filtering

[dadoonet (David Pilato)]

May be but the filtering will not happen early though. So big objects will still being built in memory.