# A couple HOWTO questions
**URL:** https://discuss.elastic.co/t/a-couple-howto-questions/60725
**Category:** Elasticsearch
**Created:** [September 16, 2016, 2:59pm UTC](https://discuss.elastic.co/t/a-couple-howto-questions/60725 "2016-09-16T14:59:32Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@DigiAngel](https://discuss.elastic.co/u/DigiAngel)
#### Post date: [September 16, 2016, 2:59pm UTC](https://discuss.elastic.co/t/a-couple-howto-questions/60725/1 "2016-09-16T14:59:32Z")
So after creating my first mapping I now discovered a few more fields that need changes. So at this point are there any HOWTO's that will explain the _process_ of mapping management? Such as:
HOWTO: Create a mapping template, apply it to all indexes, and reindex?
HOWTO: Make additions to existing mapping templates, apply to all indexes, and reindex?
Thank you.
---
### Author:  [@DigiAngel](https://discuss.elastic.co/u/DigiAngel)
#### Post date: [September 16, 2016, 5:48pm UTC](https://discuss.elastic.co/t/a-couple-howto-questions/60725/2 "2016-09-16T17:48:59Z")
Devs: This link:
[Reindex Guide](https://www.elastic.co/guide/en/elasticsearch/guide/current/reindex.html) doesn't show HOW to do anything. Why no example here?
---
### Author:  [@DigiAngel](https://discuss.elastic.co/u/DigiAngel)
#### Post date: [September 16, 2016, 6:05pm UTC](https://discuss.elastic.co/t/a-couple-howto-questions/60725/3 "2016-09-16T18:05:41Z")
And from [Updating a Mapping](https://www.elastic.co/guide/en/elasticsearch/guide/current/mapping-intro.html#updating-a-mapping):
> Although you can add to an existing mapping, you canβt change existing field mappings. If a mapping already exists for a field, data from that field has probably been indexed. If you were to change the field mapping, the indexed data would be wrong and would not be properly searchable.
why not? I'm going to have to reindex all the data anyway, why force me to most likely have to delete my entire mapping?
---
### Author:  [@kstaken](https://discuss.elastic.co/u/kstaken)
#### Post date: [September 16, 2016, 6:51pm UTC](https://discuss.elastic.co/t/a-couple-howto-questions/60725/4 "2016-09-16T18:51:23Z")
What that's referring to is changing the mapping associated with an existing index. The data has already been indexed using that mapping so changing it and then indexing more data on the changed mapping into the same index would result in inconsistent results. You can change templates all you want as they're only applied at the time an index is created.
Kimbro
---
### Author:  [@DigiAngel](https://discuss.elastic.co/u/DigiAngel)
#### Post date: [September 16, 2016, 7:36pm UTC](https://discuss.elastic.co/t/a-couple-howto-questions/60725/5 "2016-09-16T19:36:57Z")
I see that you can actually modify the template...I was expecting an error, but I was able...so that's a plus at least..thank you Kimbro.
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### Author:  [@DigiAngel](https://discuss.elastic.co/u/DigiAngel)
#### Post date: [September 16, 2016, 7:46pm UTC](https://discuss.elastic.co/t/a-couple-howto-questions/60725/6 "2016-09-16T19:46:17Z")
So apparently reindexing with 2.3 \> is as easy as this:
```
POST /_reindex
{
"source": {
"index": "twitter"
},
"dest": {
"index": "new_twitter"
}
}
```
Thank you [StackExchange](http://stackoverflow.com/questions/25144034/how-to-copy-some-elasticsearch-data-to-a-new-index) because even the latest ES [docs](https://www.elastic.co/guide/en/elasticsearch/guide/master/reindex.html) don't show this. Continuing on...
---
### Author:  [@warkolm](https://discuss.elastic.co/u/warkolm)
#### Post date: [September 16, 2016, 9:40pm UTC](https://discuss.elastic.co/t/a-couple-howto-questions/60725/7 "2016-09-16T21:40:36Z")
> [@DigiAngel](#):
>
> Thank you StackExchange because even the latest ES docs don't show this. Continuing on..
You mean like this - [Reindex API | Elasticsearch Guide [2.4] | Elastic](https://www.elastic.co/guide/en/elasticsearch/reference/2.4/docs-reindex.html)
---
### Author:  [@DigiAngel](https://discuss.elastic.co/u/DigiAngel)
#### Post date: [September 16, 2016, 9:44pm UTC](https://discuss.elastic.co/t/a-couple-howto-questions/60725/8 "2016-09-16T21:44:57Z")
Ah...LOL...I see....this is under "Document API's", not in the "Reindexing Your Data" section in the "Index Management" section...gotcha π And thanks..I'll keep posting as I continue on my journey π
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 5, 2017, 10:19pm UTC](https://discuss.elastic.co/t/a-couple-howto-questions/60725/9 "2017-07-05T22:19:30Z")