Unique key constraint and optimistic locking (versioning)

[Per Steffensen]

Hi

Does solr/lucene provide any mechanism for "unique key constraint" and 
"optimistic locking (versioning)"?
Unique key constraint: That a client will not succeed creating a new 
document in solr/lucene if a document already exists having the same 
value in some field (e.g. an id field). Of course implemented right, so 
that even though two or more threads are concurrently trying to create a 
new document with the same value in this field, only one of them will 
succeed.
Optimistic locking (versioning): That a client will only succeed 
updating a document if this updated document is based on the version of 
the document currently stored in solr/lucene. Implemented in the 
optimistic way that clients during an update have to tell which version 
of the document they fetched from Solr and that they therefore have used 
as a starting-point for their updated document. So basically having a 
version field on the document that clients increase by one before 
sending to solr for update, and some code in Solr that only makes the 
update succeed if the version number of the updated document is exactly 
one higher than the version number of the document already stored. Of 
course again implemented right, so that even though two or more thrads 
are concurrently trying to update a document, and they all have their 
updated document based on the current version in solr/lucene, only one 
of them will succeed.

Or do I have to do stuff like this myself outside solr/lucene - e.g. in 
the client using solr.

Regards, Per Steffensen