public void setRootNode(final PrintableNode rootNode) {
        this.root = rootNode;
    }
Class to hold a tree of filter terms for use in stats retrieval. Due to the
way the stats are stored (by UID) it is only possible to do equals or not
equals on an object type/value pair
stroom-statistics/stroom-statistics-impl-sql/src/main/java/stroom/statistics/impl/sql/search/FilterTermsTree.java