[Feature Request] I have multiple knn_vector fields with settings.index.knn set to true, but it would be ideal if certain fields could use approximate k-NN search while others could only use exact k-NN.

[bcc829]

Is your feature request related to a problem? Please describe

In my index, I have two knn_vector fields with settings.index.knn set to true, but I want one field to use approximate k-NN search while the other only uses exact k-NN. The field not using approximate k-NN is consuming a lot of memory. It would be ideal if I could configure the use of approximate k-NN on a per-field basis.

Describe the solution you'd like

It would be nice if it could be set for each field as shown below.

{
  "settings": {
    "index": {
      "knn": true,
    }
  },
  "mappings": {
    "properties": {
      "vector1": {
        "type": "knn_vector",
        "dimension": 2,
        "index": "false"
      },
      "vector2": {
        "type": "knn_vector",
        "dimension": 4,
        "index": "false"
      }
    }
  }
}

Related component

Search

Describe alternatives you've considered

No response

Additional context

No response

[sandeshkr419]

Does this belongs in k-nn repo - https://github.com/opensearch-project/k-NN/

cc - @navneet1v

[navneet1v]

@sandeshkr419
yes this belongs to k-NN.

@bcc829 there are already some github issues created for to exactly solve this problem: #1079, #1078

Please do a +1 on the issue and also add your use case so that it can be priortized.

cc: @vamshin

[vamshin]

@sandeshkr419 do you have permissions to move this to k-NN repo?

[sandeshkr419]

I don't have permissions to move, but @prudhvigodithi mentioned in triage meeting that he can move it (probably maintainer's permissions).

@prudhvigodithi Can you please move this to k-NN plugin?

(I'll add back the untriage label so that k-NN group can acknowledge it)