How to get ordered results from couchbase - couchbase

Question

I have in my bucket a document containing a list of ID (childList).
I would like to query over this list and keep the result ordered like in my JSON. My query is like (using java SDK) :
String query = new StringBuilder().append("SELECT B.name, META(B).id as id ")
.append("FROM" + bucket.name() + "A ")
.append("USE KEYS $id ")
.append("JOIN" + bucket.name() + "B ON KEYS ARRAY i FOR i IN A.childList end;").toString();
This query will return rows that I will transform into my domain object and create a list like this :
n1qlQueryResult.allRows().forEach(n1qlQueryRow -> (add to return list ) ...);
The problem is the output order is important.
Any ideas?
Thank you.

Answer 1

here is a rough idea of a solution without N1QL, provided you always start from a single A document:
List<JsonDocument> listOfBs = bucket
.async()
.get(idOfA)
.flatMap(doc -> Observable.from(doc.content().getArray("childList")))
.concatMapEager(id -> bucket.async().get(id))
.toList()
.toBlocking().first();
You might want another map before the toList to extract the name and id, or to perform your domain object transformation even maybe...
The steps are:
use the async API
get the A document
extract the list of children and stream these ids
asynchronously fetch each child document and stream them but keeping them in original order
collect all into a List<JsonDocument>
block until the list is ready and return that List.