Select couchbase nested object - couchbase

Question

I have a bunch of documents with a structure like this:
{
"month": 11,
"year": 2017,
//other fields
"Cars":[
{
"CarId": 123,
// other fields
},
{
"CarId": 456,
// other fields
}
// other cars
]
}
I am searching for a concrete car instance with id = 456. So far I have:
SELECT Cars
FROM DevBucket
WHERE year = 2017
AND month = 11
AND [CarId=456]
Couchbase returns correct document (which contains target car). However the output includes an array of all Car nodes within a document, but I'd like to have a single car (as if I use SELECT Cars[1] in the example above)
Search through couchbase tutorials didn't give me an answer. Is there a better way?

Answer 1

Using the UNNEST clause you can perform "a join of the nested array with its parent object." This will produce an object for each nested element that includes the nested element as a top-level field, along with the rest of the original document (nested elements, and all).
This query will retrieve the car with an id of 456 when its parent object has a month and year of 11/2017.
SELECT car
FROM DevBucket db
UNNEST Cars car
WHERE car.CarId = 456
AND db.year = 2017
AND db.month = 11;
Create this index for a quicker lookup than what you'll get with a Primary Index:
CREATE INDEX cars_index
ON DevBucket(DISTINCT ARRAY car.CarId FOR car IN Cars END);
For more information on UNNEST see NEST and UNNEST: Normalizing and Denormalizing JSON on the Fly