Get field mapping API returns empty response on wildcard-included search_as_you_type field

[tmoschou]

Elasticsearch Version

8.16.1

Installed Plugins

analysis-icu, mapper-size

Java Version

OpenJDK Runtime Environment (build 17.0.13+12-LTS)

OS Version

Linux elasticsearch-master-0 5.10.207 #1 SMP PREEMPT Tue Sep 3 18:23:52 UTC 2024 aarch64 GNU/Linux

Problem Description

Get field mapping query with a wildcard field matching any field of type search_as_you_type causes server to respond with empty response {}.

Steps to Reproduce

1. Create index

   curl -X PUT localhost:9200/my-index -H 'Content-Type: application/json' -d '
   {
       "mappings": {
           "properties": {
               "field1a": { "type": "search_as_you_type" },
               "field1b": { "type": "text" },
               "field2a": { "type": "text" },
               "field2b": { "type": "text" }
           }
       }
   }'
   

2. Query field mapping

   curl -X GET 'localhost:9200/my-index/_mapping/field/field1*'
   

   Expected behaviour

   Step 2 returns:

   {
     "my-index": {
       "mappings": {
         "field1a": {
           "full_name": "field1a",
           "mapping": {
             "field1a": {
               "type": "search_as_you_type",
               "doc_values" : false,
               "max_shingle_size" : 3
             }
           }
         },
         "field1b": {
           "full_name": "field1b",
           "mapping": {
             "field1b": {
               "type": "text"
             }
           }
         }
       }
     }
   }
   

   Actual behaviour
   Step 2 returns:

   {}
   

   Not only is field1a not returned, but neither is any other field matched (E.g. field1b, or all other fields if using /_mapping/field/* ).

3. Querying non-existing fields return differently

   curl -X GET 'localhost:9200/my-index/_mapping/field/field3*'
   {"my-index":{"mappings":{}}}
   

4. Querying the search_as_you_type exactly without wildcard does work

   curl -X GET 'localhost:9200/my-index/_mapping/field/field1a'
   {
     "my-index": {
       "mappings": {
         "field1a": {
           "full_name": "field1a",
           "mapping": {
             "field1a": {
               "type": "search_as_you_type",
               "doc_values": false,
               "max_shingle_size": 3
             }
           }
         }
       }
     }
   }
   

Logs (if relevant)

No logs lines are written

[tmoschou]

Workaround might be to use the Field Capabilities API, although it will not have some of the details of the Field Mapping API.

curl 'http://localhost:9200/my-index/_field_caps?fields=field1*'

[javanna]

Could you use the get mappings API instead?

[elasticsearchmachine]

Pinging @elastic/es-search-foundations (Team:Search Foundations)

[tmoschou]

Could you use the get mappings API instead?

Yep mapping API would work too 🙃 - with a bit more client side work for our use case. For context, our use case being we want to run Update Mapping Request in dry-run mode (or validate ahead) to know if the request would a) succeed, and b) cause a change in the mapping - dry-run doesn't seem possible, so need to query the fields in the update mapping request.