@Override
    public Result search(Query query, Execution execution) {
        QueryTree tree = query.getModel().getQueryTree();
        Item root = tree.getRoot();
        if (root != null) {
            Item newRoot = root.clone();
            newRoot = simplifyPhrases(newRoot);
            // Sets new root instead of transforming the query tree
            // to make code nicer if the root is a single term phrase
            if (!root.equals(newRoot)) {
                tree.setRoot(newRoot);
                query.trace("Collapsing single term phrases to single terms",
                    true, 2);
            }
        }
        return execution.search(query);
    }
Make single item phrases in query into single word items.

@author Steinar Knutsen
container-search/src/main/java/com/yahoo/prelude/querytransform/CollapsePhraseSearcher.java