Use variables in the missing field from group by item

Hi,

I have the following lucene Query :

ServiceName:$name OR idService:$name

because sometimes, in my datas, the ServiceName attribute is missing but is valued in the idService attribute (and I have to deal with).

I want to “group by” the results on the term field ServiceName, but the records which are missing this field are ignored.

I however can deal with them by puting a default value in the “Missing” field from the order by item.
But it seems that we can’t use variables, nor values from the result.

It would be great if I could give them the idService attribute value, so that they could be grouped as well with the others which are not missing the ServiceName attribute.

Thank you for your advices

Regards