I am setting up a Solr Search Engine that will index multiple languages. I created a custom UpdateProcessorFactory to figure out which sections of the input text are which lang
The best way is to use the DisMaxRequestHandler. It will appropriately analyze each field for the appropriate language (as defined in schema.xml).
So, if your query looks like /solr/select?qt=dismax&qf=en-text%20fr-text%20de-text&q=hello%world Solr will do the right thing.
(assuming you configured dismax as a solr.DisMaxRequestHandler in a requestHandler block in solrconfig.xml)
Most analysis is fast. Your performance bounds are mostly on your index size, total term counts, etc. Be sure to tune everything according to the solr perfomance guide on their wiki. I'm currently running a 60GB index and continue to get searches in the sub 100ms range on hardware that isn't all that fancy.