# Reindex and unique identification

**URL:** <https://discuss.elastic.co/t/reindex-and-unique-identification/191076>\
**Category:** Elasticsearch\
**Created:** [July 17, 2019, 7:43pm UTC](https://discuss.elastic.co/t/reindex-and-unique-identification/191076 "2019-07-17T19:43:36Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![xyz2](https://avatars.discourse-cdn.com/v4/letter/x/e480ec/32.png) [@xyz2](https://discuss.elastic.co/u/xyz2)\
**Post date:** [July 17, 2019, 7:43pm UTC](https://discuss.elastic.co/t/reindex-and-unique-identification/191076/1 "2019-07-17T19:43:36Z")

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Hi,

Had a question about reindexing. I executed these steps

1. Create a new index
2. Reindex to the new index
3. Did wait for 2nd step to complete then started adding more documents to the new index through logstash

In logstash I defined a unique document id . At the time of reindex, there were duplicates in source. Does at any point of time , the destination index remove the duplicates on its own (which were copied as part of step 2) ??

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [August 14, 2019, 7:43pm UTC](https://discuss.elastic.co/t/reindex-and-unique-identification/191076/2 "2019-08-14T19:43:39Z")

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