# Change document data while reindexing documents
**URL:** https://discuss.elastic.co/t/change-document-data-while-reindexing-documents/222063
**Category:** Elasticsearch
**Created:** [March 4, 2020, 11:30am UTC](https://discuss.elastic.co/t/change-document-data-while-reindexing-documents/222063 "2020-03-04T11:30:07Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Bengagi\_Foued](https://discuss.elastic.co/u/Bengagi_Foued)
#### Post date: [March 4, 2020, 11:30am UTC](https://discuss.elastic.co/t/change-document-data-while-reindexing-documents/222063/1 "2020-03-04T11:30:07Z")
i'd like to know if there is a way to ignore some fields that contains specifics values while reindexing
---
### Author:  [@Wolfram\_Haussig](https://discuss.elastic.co/u/Wolfram_Haussig)
#### Post date: [March 4, 2020, 11:38am UTC](https://discuss.elastic.co/t/change-document-data-while-reindexing-documents/222063/2 "2020-03-04T11:38:52Z")
Hi,
In other words you want to remove fields in the target index which are in the source index? While I haven't tried it out I guess this is what you want:
> ```
> POST _reindex
> {
> "source": {
> "index": "twitter",
> "_source": ["user", "_doc"]
> },
> "dest": {
> "index": "new_twitter"
> }
> }
>
> ```
> **[Reindex API | Elasticsearch Guide \[8.11\] | Elastic](https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-reindex.html#docs-reindex-filter-source)**
> `_source`
> (Optional, string) If `true` reindexes all source fields. Set to a list to reindex select fields. Defaults to `true` .
Best regards
Wolfram
---
### Author:  [@Bengagi\_Foued](https://discuss.elastic.co/u/Bengagi_Foued)
#### Post date: [March 4, 2020, 12:13pm UTC](https://discuss.elastic.co/t/change-document-data-while-reindexing-documents/222063/3 "2020-03-04T12:13:31Z")
Hi ,
i want to ignore fields based on their value , for example if date field has a specific value in the source index i'd like to put a new value for the date in the target index
---
### Author:  [@Wolfram\_Haussig](https://discuss.elastic.co/u/Wolfram_Haussig)
#### Post date: [March 4, 2020, 12:22pm UTC](https://discuss.elastic.co/t/change-document-data-while-reindexing-documents/222063/4 "2020-03-04T12:22:40Z")
Hi,
If you want to do that based on the value this is not the correct way for you. Instead, you can use a script to modify the documents before writing them to the new index:
[https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-reindex.html#reindex-scripts](https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-reindex.html#reindex-scripts)
Best regards
Wolfram
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [April 1, 2020, 12:22pm UTC](https://discuss.elastic.co/t/change-document-data-while-reindexing-documents/222063/5 "2020-04-01T12:22:51Z")
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