How to add Single-field Exemptions in Firestore Index Config File

Please let me know how to add Index exemptions for Single-field, in the firebase-indexes.json file, in order to deploy through CLI.

Currently, below is my index config in the file firebase-indexes.json, able to deploy through CLI, but it is creating an index of type Composite, not as a Single-field Exemption.

{
  "indexes": [
    {
      "collectionGroup": "comments",
      "queryScope": "COLLECTION",
      "fields": [
        {
          "fieldPath": "id",
          "order": "ASCENDING"
        },
        {
          "fieldPath": "id",
          "order": "DESCENDING"
        }
      ]
    }
  ]
}

Thanks in advance.

Assuming that your collection is called "comments" and your exemption field is called "field", you will add a new property to your firestore.indexes.json called "fieldOverrides", like this:

{
  "indexes": [
    // your indexes here
  ],
  "fieldOverrides": [
    {
      "collectionGroup": "comments",
      "fieldPath": "field",
      "indexes": [
        {
          "order": "ASCENDING",
          "queryScope": "COLLECTION"
        },
        {
          "order": "DESCENDING",
          "queryScope": "COLLECTION"
        },
        {
          "arrayConfig": "CONTAINS",
          "queryScope": "COLLECTION"
        },
        {
          "order": "ASCENDING",
          "queryScope": "COLLECTION_GROUP"
        },
        {
          "order": "DESCENDING",
          "queryScope": "COLLECTION_GROUP"
        },
        {
          "arrayConfig": "CONTAINS",
          "queryScope": "COLLECTION_GROUP"
        }
      ]
    }
  ]
}