Solr sort by min of two fields?

I want to sort a result set by the minimum of several fields.

So after reading the functionquery documentation this is what I came up with:

sort={!func}min(dvd_available_from_tdt,dto_available_from_tdt)%20desc

I also tried:

sort=_val_:min(dvd_available_from_tdt,dto_available_from_tdt)%20desc

sort=_val_:"min(dvd_available_from_tdt,dto_available_from_tdt)"%20desc

sort=_val_:"min(dvd_available_from_tdt,dto_available_from_tdt)%20desc"

sort="{!func}min(dvd_available_from_tdt,dto_available_from_tdt)"%20desc

sort={!func}min(dvd_available_from_tdt,dto_available_from_tdt)%20desc

sort="min(dvd_available_from_tdt,dto_available_from_tdt)"%20desc

and also some other placements of the quotes. But no matter what I always get this error:

HTTP ERROR: 400

Missing sort order.

Can anyobody point me in th开发者_运维问答e right direction?

Try using a query that matches all documents, with a constant score, plus a function.

http://localhost:8983/solr/select/?q=%3A+_val_:price&version=2.2&start=0&rows=10&indent=on&debugQuery=true

Also, upgrading to Solr 3.3 is not that painful, and there's all sorts of cool new toys like sorting by function.

It seems to be available only in solr 3.1. I am running 1.4.1

http://wiki.apache.org/solr/FunctionQuery#Sort_By_Function