code: public final Operation updateField(Field field) {
  
      UpdateFieldRequest request = UpdateFieldRequest.newBuilder().setField(field).build();
      return updateField(request);
    }
docs: Updates a field configuration. Currently, field updates apply only to single field index
  configuration. However, calls to
  [FirestoreAdmin.UpdateField][google.firestore.admin.v1.FirestoreAdmin.UpdateField] should
  provide a field mask to avoid changing any configuration that the caller isn't aware of. The
  field mask should be specified as: `{ paths: "index_config" }`.
  
  <p>This call returns a [google.longrunning.Operation][google.longrunning.Operation] which may
  be used to track the status of the field update. The metadata for the operation will be the
  type [FieldOperationMetadata][google.firestore.admin.v1.FieldOperationMetadata].
  
  <p>To configure the default field settings for the database, use the special `Field` with
  resource name:
  `projects/{project_id}/databases/{database_id}/collectionGroups/__default__/fields/&#42;`.
  
  <p>Sample code:
  
  <pre><code>
  try (FirestoreAdminClient firestoreAdminClient = FirestoreAdminClient.create()) {
  Field field = Field.newBuilder().build();
  Operation response = firestoreAdminClient.updateField(field);
  }
  </code></pre>
  
  @param field The field to be updated.
  @throws com.google.api.gax.rpc.ApiException if the remote call fails