unnests are not using index

cbq> CREATE INDEX join_index0 ON default(tasks_ids);
{
"request_id": "3efb1dcd-7b23-45d4-b694-d8c79815429e",
"signature": null,
"results": [
],
"status": "success",
"metrics":

{ "elapsedTime": "1.985781s", "executionTime": "1.985432s", "resultCount": 0, "resultSize": 0 }

}

cbq> EXPLAIN SELECT emp.name, task FROM default emp UNNEST emp.tasks_ids task;
{
"request_id": "69cd9e15-d624-4839-8da9-c1cc0ca6cfea",
"signature": "json",
"results": [
{
"#operator": "Sequence",
"~children": [

{ "#operator": "PrimaryScan", "index": "#primary", "keyspace": "default", "namespace": "default" }

,
{
"#operator": "Parallel",
"~child": {
"#operator": "Sequence",
"~children": [

{ "#operator": "Fetch", "as": "emp", "keyspace": "default", "namespace": "default" }

,

{ "#operator": "Unnest", "as": "task", "expr": "(`emp`.`tasks_ids`)" }

,
{
"#operator": "InitialProject",
"result_terms": [

{ "expr": "(`emp`.`name`)" }

,

{ "expr": "`task`" }

]
},

{ "#operator": "FinalProject" }

]
}
}
]
}
],
"status": "success",
"metrics":

{ "elapsedTime": "2.75ms", "executionTime": "2.3ms", "resultCount": 1, "resultSize": 1647 }

}

cbq>