# Update by query performance in single index vs multiple indices

**URL:** <https://discuss.elastic.co/t/update-by-query-performance-in-single-index-vs-multiple-indices/198711>\
**Category:** Elasticsearch\
**Created:** [September 9, 2019, 2:35pm UTC](https://discuss.elastic.co/t/update-by-query-performance-in-single-index-vs-multiple-indices/198711 "2019-09-09T14:35:52Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![kowsik](https://avatars.discourse-cdn.com/v4/letter/k/22d042/32.png) [@kowsik](https://discuss.elastic.co/u/kowsik)\
**Post date:** [September 9, 2019, 2:35pm UTC](https://discuss.elastic.co/t/update-by-query-performance-in-single-index-vs-multiple-indices/198711/1 "2019-09-09T14:35:52Z")

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I used _update by query_ to update two fields in approximately 10 million documents in a single index and it took around 21-22 minutes to get updated.

I want to know if there will be a significant difference in time taken if these 10 million documents are present in various indices ( lets say 5k documents in 2000 indices each i.e 10 million in total). If yes, will it increase or decrease by a vast difference?

It would be good to get a rough number!

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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:** [October 7, 2019, 2:35pm UTC](https://discuss.elastic.co/t/update-by-query-performance-in-single-index-vs-multiple-indices/198711/2 "2019-10-07T14:35:54Z")

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