Issue with merging queries with CB 4.6, Java 2.3.5

Couchbase Server
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1

I have some code which was working before I upgraded to Couchbase 4.6dp this morning. In doing so, I was forced to upgrade my Java Client to 2.3.5/1.3.5 and I also updated ReactiveX to 1.2.3.

There is now a much more subtle bug in this setup which appears to be connected to trying to merge the results of two asynchronous queries. I’ve managed to reproduce it in a relatively simple example based on the beer-sample, extraneous code deleted:

  	SimpleN1qlQuery q1 = N1qlQuery.simple("select name from `beer-sample` where code = '94017'");
  	SimpleN1qlQuery q2 = N1qlQuery.simple("select name from `beer-sample` where code = '94107'");
  	{
  		Observable<N1qlMetrics> mt = Observable.merge(bucket.async().query(q1), bucket.async().query(q2)).flatMap(x -> x.info());
  		BlockingObservable<Integer> map = mt.map(i -> i.resultCount()).toBlocking();
  		Iterator<Integer> it = map.getIterator();
  		while (it.hasNext())
  			System.out.println("forward, have " + it.next());
  	}
  	{
  		Observable<N1qlMetrics> mt = Observable.merge(bucket.async().query(q2), bucket.async().query(q1)).flatMap(x -> x.info());
  		BlockingObservable<Integer> map = mt.map(i -> i.resultCount()).toBlocking();
  		Iterator<Integer> it = map.getIterator();
  		while (it.hasNext())
  			System.out.println("reversed, have " + it.next());
  	}

The output from this in my environment is:

forward, have 0
forward, have 3
reversed, have 0
reversed, have 0

That is, with the queries one way around in merge(), the results come back as you would expect; with the queries the other way around, both come back as “no results found”.

I’ve tagged this primarily “Couchbase Server” because I suspect the 4.6dp, but it could be part of the Java client library or even ReactiveX.