Question regarding Solr 4.7 solr joining across multiple cores and sorting

[Parnit Pooni]

Hi,
I'm running into an issue attempting to sort, here is the scenario.

I have my mainIndex which looks something like this.

 id     description           name
  1   "description1 "    "name1"
  2   "description2 "    "name2"

I also have a subIndex which looks something like this

id   metric
1      4
2      5

What I am trying to do is join the two index's on the id column and have my
results sorted based on a column from the subIndex with a query like the
following.

testServer/solr/MainIndex/select?defType=edismax&q=*&fq={!join from=id
to=id fromIndex=subIndex}id:*&sort=metric desc

desired result

 2   "description2 "    "name2"
 1   "description1 "    "name1"

I'm aware that you lose all information from the subIndex the moment the
parser sees "&". What are my options should I want to join two indexes and
sort on a column not present in the main index?

Thanks in advance.
Parnit