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https://issues.apache.org/jira/browse/LUCENE-3201?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13052159#comment-13052159
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Robert Muir commented on LUCENE-3201:
-------------------------------------
I didnt commit because I didn't measure any performance improvements from the
patch (this frustrated me).
Also, I didn't address Uwe's last comment...
In general, I was thinking that this would be a good performance win, but it
isn't. So we should consider it from a refactoring perspective only.
> improved compound file handling
> -------------------------------
>
> Key: LUCENE-3201
> URL: https://issues.apache.org/jira/browse/LUCENE-3201
> Project: Lucene - Java
> Issue Type: Improvement
> Reporter: Robert Muir
> Fix For: 3.3, 4.0
>
> Attachments: LUCENE-3201.patch, LUCENE-3201.patch
>
>
> Currently CompoundFileReader could use some improvements, i see the following
> problems
> * its CSIndexInput extends bufferedindexinput, which is stupid for
> directories like mmap.
> * it seeks on every readInternal
> * its not possible for a directory to override or improve the handling of
> compound files.
> for example: it seems if you were impl'ing this thing from scratch, you would
> just wrap the II directly (not extend BufferedIndexInput,
> and add compound file offset X to seek() calls, and override length(). But of
> course, then you couldnt throw read past EOF always when you should,
> as a user could read into the next file and be left unaware.
> however, some directories could handle this better. for example MMapDirectory
> could return an indexinput that simply mmaps the 'slice' of the CFS file.
> its underlying bytebuffer etc naturally does bounds checks already etc, so it
> wouldnt need to be buffered, not even needing to add any offsets to seek(),
> as its position would just work.
> So I think we should try to refactor this so that a Directory can customize
> how compound files are handled, the simplest
> case for the least code change would be to add this to Directory.java:
> {code}
> public Directory openCompoundInput(String filename) {
> return new CompoundFileReader(this, filename);
> }
> {code}
> Because most code depends upon the fact compound files are implemented as a
> Directory and transparent. at least then a subclass could override...
> but the 'recursion' is a little ugly... we could still label it
> expert+internal+experimental or whatever.
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