@Override
    public AbstractArrayContext clone() {
        try {
            AbstractArrayContext clone = (AbstractArrayContext)super.clone();
            clone.indexedBindings = indexedBindings.clone();
            return clone;
        }
        catch (CloneNotSupportedException e) {
            throw new RuntimeException("Programming error");
        }
    }
Creates a clone of this context suitable for evaluating against the same ranking expression
in a different thread (i.e, name name to index map, different value set.
searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/AbstractArrayContext.java