### Author:  [@xabbu42](https://discuss.elastic.co/u/xabbu42)
#### Post date: [February 27, 2017, 6:40pm UTC](https://discuss.elastic.co/t/upgrading-index-with-custom-similarity-not-working/76678/1 "2017-02-27T18:40:46Z")
Hello
I use a custom similarity and since the switch to elasticsearch 5 I can't upgrade existing indices using this custom similarity.
The Plugin code registers the custom similarity as follows:
```
public void onIndexModule(IndexModule module) {
module.addSimilarity("searchchsimilarity", SearchChSimilarityProvider::new);
}
```
And the indices use this similarity as default by setting:
```
"settings": {
"similarity": {
"default": {
"type": "searchchsimilarity"
}
},
```
This works when creating new indices, but if I want to upgrade an index from an older elasticsearch version (either by restoring a snapshot or by starting a newer elasticsearch on the server), I get the following errors:
>
What am I doing wrong? Or is this a bug?
---
### Author:  [@xabbu42](https://discuss.elastic.co/u/xabbu42)
#### Post date: [March 2, 2017, 2:42pm UTC](https://discuss.elastic.co/t/upgrading-index-with-custom-similarity-not-working/76678/2 "2017-03-02T14:42:25Z")
No help here? There have to be others with the same problem. I'm happy to give more info if necessary or test some stuff.
---
### Author:  [@Peter\_van\_der\_Weerd](https://discuss.elastic.co/u/Peter_van_der_Weerd)
#### Post date: [March 8, 2017, 9:12pm UTC](https://discuss.elastic.co/t/upgrading-index-with-custom-similarity-not-working/76678/3 "2017-03-08T21:12:04Z")
Hi Nathan,
I did not try to upgrade, but I expect it to fail. Elastic changed the way a similarity is configured, so it might or might not succeed.
Did you check the code? I mean from the stacktrace? The inner exception states that it cannot find your similarity…
It is AFAIK configurable afterwards via a put settings. So, you could try to remove the similarity in the old ES, open it in the new ES and re-apply the similarity.
A different approach would be to just reindex the complete index.
Hope this helps a bit.
Kind regards,
Peter
---
### Author:  [@xabbu42](https://discuss.elastic.co/u/xabbu42)
#### Post date: [March 9, 2017, 2:41pm UTC](https://discuss.elastic.co/t/upgrading-index-with-custom-similarity-not-working/76678/4 "2017-03-09T14:41:45Z")
> [@Peter\_van\_der\_Weerd](#):
>
> Did you check the code? I mean from the stacktrace? The inner exception states that it cannot find your similarity…
yeah, i've seen that. the strange thing is, that I can create a new index using the very same similarity name with no problems. thats why I think that either my way of registering a custom similarity is wrong or elasticsearch 5 has a bug here.
> [@Peter\_van\_der\_Weerd](#):
>
> It is AFAIK configurable afterwards via a put settings. So, you could try to remove the similarity in the old ES, open it in the new ES and re-apply the similarity.
Thats a good idea and I will probably do an upgrade this way next week. Still that was not necessary with elasticsearch 2.4.
Thanks a lot for your answer.
Nathan
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [April 6, 2017, 2:42pm UTC](https://discuss.elastic.co/t/upgrading-index-with-custom-similarity-not-working/76678/5 "2017-04-06T14:42:13Z")
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