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From "Jason Rutherglen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1574) PooledSegmentReader, pools SegmentReader underlying byte arrays
Date Tue, 25 Jan 2011 19:35:43 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1574?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12986637#action_12986637
] 

Jason Rutherglen commented on LUCENE-1574:
------------------------------------------

bq. I think likely alloc of big BitVector, System.arraycopy, destroying it, may be a fairly
low cost compared to lucene resolving the deleted term, indexing the doc, flushing the tiny
segment, etc.

Right, and if we pool the byte[]s we'd take the cost of instantiating and GC'ing out of the
picture in the high NRT throughput case.  It's counter intuitive and will require testing.

> PooledSegmentReader, pools SegmentReader underlying byte arrays
> ---------------------------------------------------------------
>
>                 Key: LUCENE-1574
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1574
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: contrib/*
>    Affects Versions: 2.4.1
>            Reporter: Jason Rutherglen
>            Priority: Minor
>             Fix For: 4.0
>
>         Attachments: LUCENE-1574.patch
>
>   Original Estimate: 168h
>  Remaining Estimate: 168h
>
> PooledSegmentReader pools the underlying byte arrays of deleted docs and norms for realtime
search.  It is designed for use with IndexReader.clone which can create many copies of byte
arrays, which are of the same length for a given segment.  When pooled they can be reused
which could save on memory.  
> Do we want to benchmark the memory usage comparison of PooledSegmentReader vs GC?  Many
times GC is enough for these smaller objects.

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