# \[App Search\] Search and join across multiple engines

**URL:** https://discuss.elastic.co/t/app-search-search-and-join-across-multiple-engines/337333
**Category:** Elastic Search
**Tags:** elastic-app-search
**Created:** [June 30, 2023, 4:57pm UTC](https://discuss.elastic.co/t/app-search-search-and-join-across-multiple-engines/337333 "2023-06-30T16:57:55Z")
**Posts on this page:** 4
**Page:** 1

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### Author: ![ismaelalt](https://avatars.discourse-cdn.com/v4/letter/i/aeb1de/32.png) [@ismaelalt](https://discuss.elastic.co/u/ismaelalt)
#### Post date: [June 30, 2023, 4:57pm UTC](https://discuss.elastic.co/t/app-search-search-and-join-across-multiple-engines/337333/1 "2023-06-30T16:57:55Z")

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I'm using App Search. Is it possible to search and join results across two engines?

For instance, let's consider 2 indices:

```auto
exam {
    ...
}

```

```auto
exam_completion {
    exam_id: ...
    user_id: ...
}

```

Use case: I want to run a search on the `exam` engine to find exams that have been completed by a given user. Does App Search provide a solution to perform the join?

If not, I would need to have a `completion` field in the `exam` collection, but I'm not fond of this solution because the array may contain thousands of elements.

Thanks!

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### Author: ![nfeekery](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/nfeekery/32/117349_2.png) [@nfeekery](https://discuss.elastic.co/u/nfeekery)
#### Post date: [July 19, 2023, 8:27am UTC](https://discuss.elastic.co/t/app-search-search-and-join-across-multiple-engines/337333/2 "2023-07-19T08:27:23Z")

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Hi Ismaël, I think the solution you may be looking for is [meta engines](https://www.elastic.co/guide/en/enterprise-search/current/engines.html#engines-meta-engine). These will allow you to combine engines for search operations in App Search.

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<div class="post-metadata">

### Author: ![ismaelalt](https://avatars.discourse-cdn.com/v4/letter/i/aeb1de/32.png) [@ismaelalt](https://discuss.elastic.co/u/ismaelalt)
#### Post date: [August 9, 2023, 12:26pm UTC](https://discuss.elastic.co/t/app-search-search-and-join-across-multiple-engines/337333/3 "2023-08-09T12:26:14Z")

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Hi @nfeekery,

Thank you for you reply!

I don't think meta engines are designed to perform JOIN operations, but rather group multiple indexes under the same engine.

In my use case, I need to search on index exams such that there is a completion for a given user in index exam\_completion. Does that make sense?

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### Author: ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)
#### Post date: [September 6, 2023, 12:26pm UTC](https://discuss.elastic.co/t/app-search-search-and-join-across-multiple-engines/337333/4 "2023-09-06T12:26:37Z")

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