public void addSearchNode(DeployState deployState, ContentNode node, StorageGroup parentGroup, ModelElement element) {
        TreeConfigProducer<AnyConfigProducer> parent = (searchCluster != null) ? searchCluster : this;

        NodeSpec spec = getNextSearchNodeSpec(parentGroup);
        SearchNode searchNode;
        if (element == null) {
            searchNode = SearchNode.create(parent, "" + node.getDistributionKey(), node.getDistributionKey(), spec,
                                           clusterName, node, flushOnShutdown, tuning, deployState.isHosted(),
                                           fractionOfMemoryReserved, syncTransactionLog);
            searchNode.setHostResource(node.getHostResource());
            searchNode.initService(deployState);
        } else {
            searchNode = new SearchNode.Builder("" + node.getDistributionKey(), spec, clusterName, node, flushOnShutdown,
                                                tuning, fractionOfMemoryReserved, syncTransactionLog)
                    .build(deployState, parent, element.getXml());
        }
        if (searchCluster != null) {
            searchCluster.addSearcher(searchNode);
        } else {
            nonIndexed.add(searchNode);
        }
    }
Returns whether the schemas in this cluster use streaming mode.

@return True if this cluster only has schemas with streaming mode, False if it only has schemas
        with indexing, null if it has both or none.
config-model/src/main/java/com/yahoo/vespa/model/content/ContentSearchCluster.java