# Whether rrf can be applied to nested knn search using inner hits

**URL:** <https://discuss.elastic.co/t/whether-rrf-can-be-applied-to-nested-knn-search-using-inner-hits/352737>\
**Category:** Elasticsearch\
**Tags:** vector-search\
**Created:** [February 7, 2024, 10:53am UTC](https://discuss.elastic.co/t/whether-rrf-can-be-applied-to-nested-knn-search-using-inner-hits/352737 "2024-02-07T10:53:44Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![shwanlee](https://avatars.discourse-cdn.com/v4/letter/s/e9bcb4/32.png) [@shwanlee](https://discuss.elastic.co/u/shwanlee)\
**Post date:** [February 7, 2024, 10:53am UTC](https://discuss.elastic.co/t/whether-rrf-can-be-applied-to-nested-knn-search-using-inner-hits/352737/1 "2024-02-07T10:53:44Z")

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Does rrf apply to queries that combine keyword search, sparse vector search, and knn vector search using inner hits?

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**Author:** ![iulia](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/iulia/32/124658_2.png) [@iulia](https://discuss.elastic.co/u/iulia)\
**Post date:** [March 3, 2024, 3:07pm UTC](https://discuss.elastic.co/t/whether-rrf-can-be-applied-to-nested-knn-search-using-inner-hits/352737/2 "2024-03-03T15:07:35Z")

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Hi!

At the moment on the official docs it says the current (technical preview) supports the following types of searches:

RRF does support:

- [sub searches](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-search.html#request-body-sub-searches)
- [aggregations](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations.html)
- [from](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-search.html#search-from-param)

> You can use RRF as part of a [search](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-search.html) to combine and rank documents using result sets from a combination of [query](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-search.html#request-body-search-query), [sub searches](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-search.html#request-body-sub-searches), and/or [knn searches](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-search.html#search-api-knn). A minimum of 2 results sets is required for ranking from the specified sources.

[Check the docs for examples.](https://www.elastic.co/guide/en/elasticsearch/reference/current/rrf.html#rrf-supported-features)

The capabilities may change and evolve until it reaches GA - you can test it out; any unsupported features included in the query will result in an exception.

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [March 31, 2024, 3:07pm UTC](https://discuss.elastic.co/t/whether-rrf-can-be-applied-to-nested-knn-search-using-inner-hits/352737/3 "2024-03-31T15:07:47Z")

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