@Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        IndexableFeatureConjunction that = (IndexableFeatureConjunction) o;
        return id == that.id;
    }
K value - number of non-negated operands
predicate-search/src/main/java/com/yahoo/search/predicate/index/conjunction/IndexableFeatureConjunction.java