# Reindex with mapping of data

**URL:** <https://discuss.elastic.co/t/reindex-with-mapping-of-data/226692>\
**Category:** Elasticsearch\
**Created:** [April 6, 2020, 11:31am UTC](https://discuss.elastic.co/t/reindex-with-mapping-of-data/226692 "2020-04-06T11:31:40Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![yBother](https://avatars.discourse-cdn.com/v4/letter/y/e274bd/32.png) [@yBother](https://discuss.elastic.co/u/yBother)\
**Post date:** [April 6, 2020, 11:31am UTC](https://discuss.elastic.co/t/reindex-with-mapping-of-data/226692/1 "2020-04-06T11:31:41Z")

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I am using high level NEST client for C# version 7.6.0.  
I want to migrate existing data created in 5.2 to 7.6.0  
I understand that I need to migrate to version 6.x (6.8) first.

The only thing I found was this:

```auto

 var reindexResponse = this.ElasticClient.ReindexOnServer(r => r
                        .Source(s => s
                            .Index(indexName)
                        )
                        .Destination(d => d
                            .Index(newIndexName)
                        ).Refresh(false)
                        .WaitForCompletion(true)
                    );

```

How could I do a mapping here? I want to modify the actual data set during reindexing, if possible. Otherwise I would have to do this afterwads.  
What part is .Refresh() playing here? How would I tweak this for potentially large data sets?

---

<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:** [May 4, 2020, 11:31am UTC](https://discuss.elastic.co/t/reindex-with-mapping-of-data/226692/2 "2020-05-04T11:31:50Z")

</div>

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