Multipart documents with different update cycles

[Aurélien MAZOYER]

Hello,

I have to index a dataset containing multipart documents. The "main" 
part and the "user metadata" part have different update cycles : we want 
to update the "user metadata part" frequently without having to refetch 
the main part from the datasource nor storing every fields in order to 
use atomic update. As there is no true field level update in Solr yet, I 
am afraid that I have to build an index for both parts and to perform a 
query time join, with all the well-known performance limitation. I have 
also heard of side car index. Is it a solution that can meet my 
requirements? Is it stable enough to be usable in production? Does the 
community plan to make it part of the trunk code?

Thanks,

Aurelien