Function when

src/QLPlan.actor.cpp:704–707

			try {
				loop choose {
					when(Reference<ScanReturnedContext> doc = waitNext(docs)) {
						// throws end_of_stream when totally finished
						bufferedDocs.push_back(std::make_pair(doc, outerLock->take(g_network->getCurrentTask() + 1)));
					}
					when(wait(bufferedDocs.empty() ? Never() : bufferedDocs.front().second)) {
						innerLock->release();
						output.send(bufferedDocs.front().first);