# What happens to copy\_to field when one of the origins values modified/deleted **URL:** \ **Category:** Elasticsearch\ **Created:** [November 11, 2020, 12:44pm UTC](https://discuss.elastic.co/t/what-happens-to-copy-to-field-when-one-of-the-origins-values-modified-deleted/255060 "2020-11-11T12:44:58Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![jac1241](https://avatars.discourse-cdn.com/v4/letter/j/8baadc/32.png) [@jac1241](https://discuss.elastic.co/u/jac1241)\ **Post date:** [November 11, 2020, 12:44pm UTC](https://discuss.elastic.co/t/what-happens-to-copy-to-field-when-one-of-the-origins-values-modified-deleted/255060/1 "2020-11-11T12:44:58Z")
Hello, I didn't find any reference in docs for this question. I want to use copy\_to to copy multiple fields to a signle field, when one of the original fields might be modified. For example: I have 2 fields: ``` user_tags - which has value of ["user tag 1", "user tag2"] backend_tags - which has the value of ["be tag 1", "be tag 2"] ``` both of them copied with copy\_to to the field tags: `tags - which has the value ["user tag1", "user tag 2", "be tag 1", "be tag 2"]` 3 questions - 1. What will happen to "tags" field if someone update "user\_tags" field and remove "user tag 1", or add "user tag 3" ? 2. What will happen to "tags" field if in both "backend\_tags" and "user\_tags" there are the same tag "generic tag" ? 3. What will happen to "tags" field if this "generic tag" which was copied, will be removed from "'user\_tags" but will remain in "backend\_tags" ? Thanks 🙂 ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [December 9, 2020, 12:45pm UTC](https://discuss.elastic.co/t/what-happens-to-copy-to-field-when-one-of-the-origins-values-modified-deleted/255060/2 "2020-12-09T12:45:04Z")
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