Synonyms and Fuzziness conflict

Elastic Stack Elasticsearch
2

Hello Guilherme,

The problem is not really related to fuzzyness. You can verify this by doing a test with Fuzzy Query and you will see that you can not reproduce this.

The issue here is related to Multi Match Query. It seems that when it finds a mapped synonym it completely disregards the fuzzyness. You can verify this using the Validate API with the rewrite option. For instance:

GET <index_name>/_validate/query?rewrite=true
{
  "query": {
    "multi_match" : {
      "query":  "shirts", 
      "fields": [ "names^3", "tags_names^2" ],
      "fuzziness": "AUTO"
    }
  }
}

Do this with shirts and shirt. You will see that while the former will be rewritten using fuzzyness, the latter will actually use synonym without any fuzzyness.

TBH, I don't know why this happens (could be a bug?). Maybe @Adrien_Grand has more to tell?

Cheers