Re: Unique key constraint and optimistic locking (versioning)

[Per Steffensen]

Created SOLR-3173 on the part about making insert fail if document (with 
same uniqueKey) already exists. SOLR-3173 also includes to make "update" 
not insert document if not already exists - just for consistency with 
normal RDBMS behaviour. So basically the feature allowes you to turn on 
this behaviour of having "database" (RDBMS) semantics, and when you do 
you get both.
Tomorrrow will create another Jira issue on the "versioning/optimistic 
locking" part.

Per Steffensen skrev:
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