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From "Marvin Humphrey (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2345) Make it possible to subclass SegmentReader
Date Fri, 26 Mar 2010 21:22:27 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2345?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12850356#action_12850356
] 

Marvin Humphrey commented on LUCENE-2345:
-----------------------------------------

> Is there a ticket or wiki page that details the "plugin" architecture/design
> so i could take a look?

FWIW, KinoSearch has a complete prototype implementation of this design, 
based loosely on the mailing list conversations that Earwin referred to.

  * SegReader and SegWriter are both composites with minimal APIs.
  * All subcomponents subclass either DataWriter or DataReader.
  * The Architecture class (under KinoSearch::Plan) determines which plugins
    get loaded.

[http://www.rectangular.com/svn/kinosearch/trunk/core/]

> Make it possible to subclass SegmentReader
> ------------------------------------------
>
>                 Key: LUCENE-2345
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2345
>             Project: Lucene - Java
>          Issue Type: Wish
>          Components: Index
>            Reporter: Tim Smith
>             Fix For: 3.1
>
>         Attachments: LUCENE-2345_3.0.patch, LUCENE-2345_3.0.plugins.patch
>
>
> I would like the ability to subclass SegmentReader for numerous reasons:
> * to capture initialization/close events
> * attach custom objects to an instance of a segment reader (caches, statistics, so on
and so forth)
> * override methods on segment reader as needed
> currently this isn't really possible
> I propose adding a SegmentReaderFactory that would allow creating custom subclasses of
SegmentReader
> default implementation would be something like:
> {code}
> public class SegmentReaderFactory {
>   public SegmentReader get(boolean readOnly) {
>     return readOnly ? new ReadOnlySegmentReader() : new SegmentReader();
>   }
>   public SegmentReader reopen(SegmentReader reader, boolean readOnly) {
>     return newSegmentReader(readOnly);
>   }
> }
> {code}
> It would then be made possible to pass a SegmentReaderFactory to IndexWriter (for pooled
readers) as well as to SegmentReader.get() (DirectoryReader.open, etc)
> I could prepare a patch if others think this has merit
> Obviously, this API would be "experimental/advanced/will change in future"

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