@Override
    public Set<RankSetting> rankSettings() {
        Set<RankSetting> settings = new LinkedHashSet<>(20);
        settings.addAll(this.rankSettings);
        for (ImmutableSDField field : schema().allConcreteFields() ) {
            addSetting(field, RankSetting.Type.WEIGHT, settings);
            addSetting(field, RankSetting.Type.RANKTYPE, settings);
            addSetting(field, RankSetting.Type.LITERALBOOST, settings);
            addSetting(field, RankSetting.Type.PREFERBITVECTOR, settings);
        }

        // For settings that really pertains to indexes do the explicit indexes too
        for (Index index : schema().getExplicitIndices()) {
            addSetting(index, RankSetting.Type.PREFERBITVECTOR, settings);
        }
        return settings;
    }
Returns the names of the fields which have a rank boost setting
explicitly in this profile or in fields
config-model/src/main/java/com/yahoo/schema/DefaultRankProfile.java