Decoding failure when deleting documents

[Sembiance]

Describe the bug
Attempting to delete any document from a dataset below results in an error:

  {
    "status": "failed",
    "updateId": 2,
    "type": {
      "name": "DocumentsDeletion",
      "number": 1
    },
    "message": "internal: decoding failed",
    "errorCode": "internal",
    "errorType": "internal_error",
    "errorLink": "https://docs.meilisearch.com/errors#internal",
    "duration": 0.0,
    "enqueuedAt": "2021-08-20T01:05:08.859222412Z",
    "processedAt": "2021-08-20T01:05:08.860058643Z"
  }

To Reproduce

1. Run meilisearch v0.21.0rc6
2. Create the index :
   curl -X POST 'http://localhost:7700/indexes' --data '{"uid": "test", "primaryKey": "docid"}'
curl -X POST 'http://localhost:7700/indexes/test/settings' --data '{"filterableAttributes": ["label"]}'
3. Populate the data:

curl -X POST 'http://localhost:7700/indexes/test/documents' --data '[
	{"docid":"1_4","label":"sign"},
	{"docid":"1_5","label":"letter"},
	{"docid":"1_7","label":"abstract,cartoon,design,pattern"},
	{"docid":"1_36","label":"drawing,painting,pattern"},
	{"docid":"1_37","label":"art,drawing,outdoor"},
	{"docid":"1_38","label":"aquarium,art,drawing"},
	{"docid":"1_39","label":"abstract"},
	{"docid":"1_40","label":"cartoon"},
	{"docid":"1_41","label":"art,drawing"},
	{"docid":"1_42","label":"art,pattern"},
	{"docid":"1_43","label":"abstract,art,drawing,pattern"},
	{"docid":"1_44","label":"drawing"},
	{"docid":"1_45","label":"art"},
	{"docid":"1_46","label":"abstract,colorfulness,pattern"},
	{"docid":"1_47","label":"abstract,pattern"},
	{"docid":"1_52","label":"abstract,cartoon"},
	{"docid":"1_57","label":"abstract,drawing,pattern"},
	{"docid":"1_58","label":"abstract,art,cartoon"},
	{"docid":"1_68","label":"design"},
	{"docid":"1_69","label":"geometry"}]'

4. Attempt to delete any document: curl -X DELETE 'http://localhost:7700/indexes/test/documents/1_4'
5. Check the status, see it failed: curl -X GET 'http://localhost:7700/indexes/test/updates'

Expected behavior
I expect it not to fail.

MeiliSearch version: v0.21.0rc6
Works fine with v0.20.0

Additional context
If you skip modifying the filterableAttributes index settings, then it works ok. So it must have something to do with that.
Note, if you change it to "filterableAttributes": ["doc_id"] it still fails with the same internal: decoding failed error

[curquiza]

Hello @Sembiance! Thank you so much for this report and for the detailed steps! 🙏 I think this is the same bug as #1594 we did not succeed to reproduce!

I followed your steps and I got the same error as you report!
We'll fix this for v0.21.0

[curquiza]

Closed by #1605