# Mutate filter Join question
**URL:** https://discuss.elastic.co/t/mutate-filter-join-question/178705
**Category:** Logstash
**Created:** [April 26, 2019, 6:08pm UTC](https://discuss.elastic.co/t/mutate-filter-join-question/178705 "2019-04-26T18:08:08Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@arisbanach](https://discuss.elastic.co/u/arisbanach)
#### Post date: [April 26, 2019, 6:08pm UTC](https://discuss.elastic.co/t/mutate-filter-join-question/178705/1 "2019-04-26T18:08:08Z")
[https://www.elastic.co/guide/en/logstash/current/plugins-filters-mutate.html#plugins-filters-mutate-join](https://www.elastic.co/guide/en/logstash/current/plugins-filters-mutate.html#plugins-filters-mutate-join)
Does this only work for arrays of strings? What would happen is I tried to Join an array of objects? or an array of arrays?
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### Author:  [@Badger](https://discuss.elastic.co/u/Badger)
#### Post date: [April 27, 2019, 12:21pm UTC](https://discuss.elastic.co/t/mutate-filter-join-question/178705/2 "2019-04-27T12:21:58Z")
Provided it is passed an [array](https://github.com/logstash-plugins/logstash-filter-mutate/blob/091207d5184af1f38626c9e24cce070674a410f5/lib/logstash/filters/mutate.rb#L484) it will to\_s the members and concatenate the results.
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [May 25, 2019, 12:22pm UTC](https://discuss.elastic.co/t/mutate-filter-join-question/178705/3 "2019-05-25T12:22:00Z")
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