overwirite if not already in index?

[eks dev <ek...@googlemail.com>]

Quick question,
Is there a way with solr to conditionally update document on unique
id? Meaning, default, add behavior if id is not already in index and
*not to touch index" if already there.

Deletes are not important (no sync issues).

I am asking because I noticed with deduplication turned on,
index-files get modified even if I update the same documents again
(same signatures).
I am facing very high dupes rate (40-50%), and setup is going to be
master-slave with high commit rate (requirement is to reduce
propagation latency for updates). Having unnecessary index
modifications is going to waste  "effort" to ship the same information
again and again.

if there is no standard way, what would be the fastest way to check if
Term exists in index from UpdateRequestProcessor?

I intend to extend SignatureUpdateProcessor to prevent a document from
propagating down the chain if this happens?
Would that be a way to deal with it? I repeat, there are no deletes to
make headaches with synchronization


Thanks,
eks