Streaming evaluators - exists

[Susmit Shukla <sh...@gmail.com>]

Hi,

I need to annotate the documents matching a simple boolean "OR" query
with actual terms found in each document. It is possible in single pass
using exists() function in fl param with /select handler.
e.g
q=text:(val1 OR val2 OR val3)
&fl=foo1:exists(query({!v='text:(val1)'})),foo2:exists(query({!v='text:(val2)'})),foo3:termfreq(content,'val3')

Can the same thing be achieved using /stream and /export handlers? Any
pointers to create custom term frequency or term exist stream evaluator
would be useful.