Add MergePolicy to IndexWriterConfig
------------------------------------

                 Key: LUCENE-2320
                 URL: https://issues.apache.org/jira/browse/LUCENE-2320
             Project: Lucene - Java
          Issue Type: Improvement
          Components: Index
            Reporter: Shai Erera
             Fix For: 3.1


Now that IndexWriterConfig is in place, I'd like to move MergePolicy to it as 
well. The change is not straightforward and so I've kept it for a separate 
issue. MergePolicy requires in its ctor an IndexWriter, however none can be 
passed to it before an IndexWriter actually exists. And today IW may create an 
MP just for it to be overridden by the application one line afterwards. I don't 
want to make iw member of MP non-final, or settable by extending classes, 
however it needs to remain protected so they can access it directly. So the 
proposed changes are:

* Add a SetOnce object (to o.a.l.util), or Immutable, which can only be set 
once (hence its name). It'll have the signature SetOnce<T> w/ *synchronized 
set<T>* and *T get()*. T will be declared volatile, so that get() won't be 
synchronized.
* MP will define a *protected final SetOnce<IndexWriter> writer* instead of the 
current writer. *NOTE: this is a bw break*. any suggestions are welcomed.
* MP will offer a public default ctor, together with a set(IndexWriter).
* IndexWriter will set itself on MP using set(this). Note that if set will be 
called more than once, it will throw an exception (AlreadySetException - or 
does someone have a better suggestion, preferably an already existing Java 
exception?).

That's the core idea. I'd like to post a patch soon, so I'd appreciate your 
review and proposals.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscr...@lucene.apache.org
For additional commands, e-mail: java-dev-h...@lucene.apache.org

Reply via email to