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Date: Wed, 13 Jan 2010 14:49:54 +0000 (UTC)
From: "Aaron McCurry (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-2205) Rework of the TermInfosReader class
 to remove the Terms[], TermInfos[], and the index pointer long[] and create
 a more memory efficient data structure.
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    [ https://issues.apache.org/jira/browse/LUCENE-2205?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12799772#action_12799772 ] 

Aaron McCurry commented on LUCENE-2205:
---------------------------------------

I took a look at that class, and it does look somewhat similar.  Has anyone run any numbers against it to see that savings or performance of it?  I'm at work now, but I may try it out in my tests when I get home.

> Rework of the TermInfosReader class to remove the Terms[], TermInfos[], and the index pointer long[] and create a more memory efficient data structure.
> -------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-2205
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2205
>             Project: Lucene - Java
>          Issue Type: Improvement
>         Environment: Java5
>            Reporter: Aaron McCurry
>         Attachments: patch-final.txt, RandomAccessTest.java, rawoutput.txt
>
>
> Basically packing those three arrays into a byte array with an int array as an index offset.  
> The performance benefits are stagering on my test index (of size 6.2 GB, with ~1,000,000 documents and ~175,000,000 terms), the memory needed to load the terminfos into memory were reduced to 17% of there original size.  From 291.5 MB to 49.7 MB.  The random access speed has been made better by 1-2%, load time of the segments are ~40% faster as well, and full GC's on my JVM were made 7 times faster.
> I have already performed the work and am offering this code as a patch.  Currently all test in the trunk pass with this new code enabled.  I did write a system property switch to allow for the original implementation to be used as well.
> -Dorg.apache.lucene.index.TermInfosReader=default or small
> I have also written a blog about this patch here is the link.
> http://www.nearinfinity.com/blogs/aaron_mccurry/my_first_lucene_patch.html

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