# Merging multiple logstash output document into one by a common field
**URL:** https://discuss.elastic.co/t/merging-multiple-logstash-output-document-into-one-by-a-common-field/161944
**Category:** Logstash
**Created:** [December 23, 2018, 8:14am UTC](https://discuss.elastic.co/t/merging-multiple-logstash-output-document-into-one-by-a-common-field/161944 "2018-12-23T08:14:21Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@abhishek021](https://discuss.elastic.co/u/abhishek021)
#### Post date: [December 23, 2018, 8:14am UTC](https://discuss.elastic.co/t/merging-multiple-logstash-output-document-into-one-by-a-common-field/161944/1 "2018-12-23T08:14:21Z")
Hi,
I'm a beginner to logstash. I have created multiple documents based on some grok pattern for a particular log event.
Now, before passing documents to elastic search I want to merge those documents having common field into a single document.I'm not sure if I can do this using aggregate filter.
So either I can combine similar log events into a single log or I can merge similar output documents into one document.
Which is better and How can I achieve this ?
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [January 20, 2019, 8:28am UTC](https://discuss.elastic.co/t/merging-multiple-logstash-output-document-into-one-by-a-common-field/161944/2 "2019-01-20T08:28:37Z")
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