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From "Shai Erera (JIRA)" <>
Subject [jira] Created: (LUCENE-2574) Optimize copies between IndexInput and Output
Date Wed, 28 Jul 2010 19:17:15 GMT
Optimize copies between IndexInput and Output

                 Key: LUCENE-2574
             Project: Lucene - Java
          Issue Type: Improvement
          Components: Store
            Reporter: Shai Erera
            Assignee: Shai Erera
             Fix For: 3.1, 4.0

We've created an optimized copy of files from Directory to Directory. We've also optimized
copyBytes recently. However, we're missing the opposite side of the copy - from IndexInput
to Output. I'd like to mimic the FileChannel API by having copyTo on IndexInput and copyFrom
on IndexOutput. That way, both sides can optimize the copy process, depending on the type
of the IndexInput/Output that they need to copy to/from.

FSIndexInput/Output can use FileChannel if the two are FS types. RAMInput/OutputStream can
copy to/from the buffers directly, w/o going through intermediate ones. Actually, for RAMIn/Out
this might be a big win, because it doesn't care about the type of IndexInput/Output given
- it just needs to copy to its buffer directly.

If we do this, I think we can consolidate all Dir.copy() impls down to one (in Directory),
and rely on the In/Out ones to do the optimized copy. Plus, it will enable someone to do optimized
copies between In/Out outside the scope of Directory.

If this somehow turns out to be impossible, or won't make sense, then I'd like to optimize
RAMDirectory.copy(Dir, src, dest) to not use an intermediate buffer.

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