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From "Jason Rutherglen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2680) Improve how IndexWriter flushes deletes against existing segments
Date Mon, 22 Nov 2010 01:59:14 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2680?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12934381#action_12934381
] 

Jason Rutherglen commented on LUCENE-2680:
------------------------------------------

Running TestStressIndexing2 500 times on trunk causes this error which is probably intermittent:

{code}
[junit] Testsuite: org.apache.lucene.index.TestStressIndexing2
    [junit] Testcase: testMultiConfigMany(org.apache.lucene.index.TestStressIndexing2):	Caused
an ERROR
    [junit] Array index out of range: 0
    [junit] java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 0
    [junit] 	at java.util.Vector.get(Vector.java:721)
    [junit] 	at org.apache.lucene.index.DocumentsWriter.applyDeletes(DocumentsWriter.java:1049)
    [junit] 	at org.apache.lucene.index.IndexWriter.applyDeletes(IndexWriter.java:4291)
    [junit] 	at org.apache.lucene.index.IndexWriter.doFlushInternal(IndexWriter.java:3444)
    [junit] 	at org.apache.lucene.index.IndexWriter.doFlush(IndexWriter.java:3279)
    [junit] 	at org.apache.lucene.index.IndexWriter.flush(IndexWriter.java:3269)
    [junit] 	at org.apache.lucene.index.IndexWriter.closeInternal(IndexWriter.java:1760)
    [junit] 	at org.apache.lucene.index.IndexWriter.close(IndexWriter.java:1723)
    [junit] 	at org.apache.lucene.index.IndexWriter.close(IndexWriter.java:1687)
    [junit] 	at org.apache.lucene.index.TestStressIndexing2.indexRandom(TestStressIndexing2.java:233)
    [junit] 	at org.apache.lucene.index.TestStressIndexing2.testMultiConfig(TestStressIndexing2.java:123)
    [junit] 	at org.apache.lucene.index.TestStressIndexing2.testMultiConfigMany(TestStressIndexing2.java:97)
    [junit] 	at org.apache.lucene.util.LuceneTestCase$LuceneTestCaseRunner.runChild(LuceneTestCase.java:950)
    [junit] 	at org.apache.lucene.util.LuceneTestCase$LuceneTestCaseRunner.runChild(LuceneTestCase.java:888)
{code}

> Improve how IndexWriter flushes deletes against existing segments
> -----------------------------------------------------------------
>
>                 Key: LUCENE-2680
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2680
>             Project: Lucene - Java
>          Issue Type: Improvement
>            Reporter: Michael McCandless
>             Fix For: 4.0
>
>         Attachments: LUCENE-2680.patch, LUCENE-2680.patch, LUCENE-2680.patch, LUCENE-2680.patch,
LUCENE-2680.patch, LUCENE-2680.patch, LUCENE-2680.patch, LUCENE-2680.patch, LUCENE-2680.patch,
LUCENE-2680.patch
>
>
> IndexWriter buffers up all deletes (by Term and Query) and only
> applies them if 1) commit or NRT getReader() is called, or 2) a merge
> is about to kickoff.
> We do this because, for a large index, it's very costly to open a
> SegmentReader for every segment in the index.  So we defer as long as
> we can.  We do it just before merge so that the merge can eliminate
> the deleted docs.
> But, most merges are small, yet in a big index we apply deletes to all
> of the segments, which is really very wasteful.
> Instead, we should only apply the buffered deletes to the segments
> that are about to be merged, and keep the buffer around for the
> remaining segments.
> I think it's not so hard to do; we'd have to have generations of
> pending deletions, because the newly merged segment doesn't need the
> same buffered deletions applied again.  So every time a merge kicks
> off, we pinch off the current set of buffered deletions, open a new
> set (the next generation), and record which segment was created as of
> which generation.
> This should be a very sizable gain for large indices that mix
> deletes, though, less so in flex since opening the terms index is much
> faster.

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