private void addRankTerms(Query query, IndexFacts.Session indexFacts) {
        RankItem newRankTerms = new RankItem();
        addLiterals(newRankTerms, query.getModel().getQueryTree().getRoot(), indexFacts);
        if (newRankTerms.getItemCount() > 0)
            addTopLevelRankTerms(newRankTerms, query);

        if (query.getTrace().getLevel() >= 2 && newRankTerms.getItemCount() > 0)
            query.trace("Added rank terms for possible literal field matches.", true, 2);
    }
Adds rank terms to boost hits matching exact literals fields using info
from indexing commands.

@author bratseth
container-search/src/main/java/com/yahoo/prelude/querytransform/LiteralBoostSearcher.java