Yes, SOLR-139 will eventually do what you need.
The most recent patch should not be *too* hard to get running (it may
not apply cleanly though) The patch as is needs to be reworked before
it will go into trunk. I hope this will happen in the next month or so.
As for production? It depends ;) The API will most likely change so
if you base your code on the current patch, it will need to change
when things finalize. As for stability, it has worked well for me
(and I think for Erik)
A useful feature would be "update based on query", so that documents
matching the query condition will all be modified in the same way on the
given update fields.
If this feature also available in future?
