# Slice dense vector contents?
**URL:** https://discuss.elastic.co/t/slice-dense-vector-contents/307972
**Category:** Elasticsearch
**Created:** [June 23, 2022, 9:18am UTC](https://discuss.elastic.co/t/slice-dense-vector-contents/307972 "2022-06-23T09:18:09Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@lz-mn](https://discuss.elastic.co/u/lz-mn)
#### Post date: [June 23, 2022, 9:18am UTC](https://discuss.elastic.co/t/slice-dense-vector-contents/307972/1 "2022-06-23T09:18:09Z")
Hi,
I have about a million documents indexed with a dense vector. I am trying to add a new field to each document with a slice of its vector, e.g. the first 700 elements only. What is the best way to do this please?
The reason is so I can use the ANN search functionality with the truncated vectors.
Thank you!
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### Author:  [@mayya](https://discuss.elastic.co/u/mayya)
#### Post date: [June 27, 2022, 8:15pm UTC](https://discuss.elastic.co/t/slice-dense-vector-contents/307972/2 "2022-06-27T20:15:43Z")
If you just going to use the new field in your searches, the best way is to create a new index with a new dense\_vector field, and index modified vectors into it. The modification you can do on your application side.
If you are going to use both fields: new and old, then you need to reindex the whole index. You can use [script](https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-reindex.html#docs-reindex-change-name) to modify the content of your vectors.
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### Author:  [@lz-mn](https://discuss.elastic.co/u/lz-mn)
#### Post date: [June 28, 2022, 8:39am UTC](https://discuss.elastic.co/t/slice-dense-vector-contents/307972/3 "2022-06-28T08:39:25Z")
Thank you Mayya!
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 26, 2022, 8:40am UTC](https://discuss.elastic.co/t/slice-dense-vector-contents/307972/4 "2022-07-26T08:40:08Z")
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