# About Terms lookup mechanism peformance

**URL:** <https://discuss.elastic.co/t/about-terms-lookup-mechanism-peformance/79666>\
**Category:** Elasticsearch\
**Created:** [March 23, 2017, 1:36am UTC](https://discuss.elastic.co/t/about-terms-lookup-mechanism-peformance/79666 "2017-03-23T01:36:23Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![toka](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/toka/32/15773_2.png) [@toka](https://discuss.elastic.co/u/toka)\
**Post date:** [March 23, 2017, 1:36am UTC](https://discuss.elastic.co/t/about-terms-lookup-mechanism-peformance/79666/1 "2017-03-23T01:36:23Z")

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Hi all!

Terms Query performance problems are spoken in this [issue](https://github.com/elastic/elasticsearch/issues/18829), but I was wondering if this would be applied in case of a Terms Query using the [lookup](https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-terms-query.html#query-dsl-terms-lookup) mechanism as well.

In the docs it says:

`When it’s needed to specify a terms filter with a lot of terms it can be beneficial to fetch those term values from a document in an index.`

But not sure how much is that `a lot`.

Planning to do an stress test, but I would like to know if someone had experience with thousands of terms using lookup.

Cheers!

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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:** [April 20, 2017, 1:36am UTC](https://discuss.elastic.co/t/about-terms-lookup-mechanism-peformance/79666/2 "2017-04-20T01:36:37Z")

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