@Override
    protected void onDeserialize(Deserializer buf) {
        maxGroups = buf.getLong(null);
        precision = buf.getLong(null);
        classify = (ExpressionNode)deserializeOptional(buf);
        if (v2) {
            filter = (FilterExpressionNode) deserializeOptional(buf);
        }
        collect.deserializeWithId(buf);
    }
<p>Tell if ordering will need results collected in children.</p>

@return If deeper resultcollection is needed.
searchlib/src/main/java/com/yahoo/searchlib/aggregation/GroupingLevel.java