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From "Ning Li (JIRA)" <>
Subject [jira] Updated: (LUCENE-528) Optimization for IndexWriter.addIndexes()
Date Tue, 24 Oct 2006 22:27:18 GMT
     [ ]

Ning Li updated LUCENE-528:

    Attachment: AddIndexesNoOptimize.patch

This patch implements addIndexesNoOptimize() following the algorithm described earlier.
  - The patch is based on the latest version from trunk.
  - AddIndexesNoOptimize() is implemented. The algorithm description is included as comment
and the code is commented.
  - The patch includes a test called TestAddIndexesNoOptimize which covers all the code in
  - maybeMergeSegments() was conservative and checked for more merges only when "upperBound
* mergeFactor <= maxMergeDocs". Change it to check for more merges when "upperBound <
  - Minor changes in TestIndexWriterMergePolicy to better verify merge invariants.
  - The patch passes all unit tests.

One more comment on the implementation:
  - When we copy un-merged segments from S in step 4, ideally, we want to simply copy
    those segments. However, directory does not support copy yet. In addition, source may
    use compound file or not and target may use compound file or not. So we use
    mergeSegments() to copy each segment, which may cause doc count to change
    because deleted docs are garbage collected. That case is handled properly.  

> Optimization for IndexWriter.addIndexes()
> -----------------------------------------
>                 Key: LUCENE-528
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Steven Tamm
>         Assigned To: Otis Gospodnetic
>            Priority: Minor
>         Attachments: AddIndexes.patch, AddIndexesNoOptimize.patch
> One big performance problem with IndexWriter.addIndexes() is that it has to optimize
the index both before and after adding the segments.  When you have a very large index, to
which you are adding batches of small updates, these calls to optimize make using addIndexes()
impossible.  It makes parallel updates very frustrating.
> Here is an optimized function that helps out by calling mergeSegments only on the newly
added documents.  It will try to avoid calling mergeSegments until the end, unless you're
adding a lot of documents at once.
> I also have an extensive unit test that verifies that this function works correctly if
people are interested.  I gave it a different name because it has very different performance
characteristics which can make querying take longer.

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