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Date: Fri, 14 Oct 2005 05:27:08 +0200 (CEST)
From: "Yonik Seeley (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org
Subject: [jira] Updated: (LUCENE-454) lazily create SegmentMergeInfo.docMap
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     [ http://issues.apache.org/jira/browse/LUCENE-454?page=all ]

Yonik Seeley updated LUCENE-454:
--------------------------------

    Attachment: docMap.txt

Also deferred creation of SegmentMergeInfo.postings (TermPositions) for another 15% gain.

Same index and query were used to test, but this time 100,000 query iterations.

defer docMap only:
  indexing time = 121,734 ms
  querying time = 18,266 ms

defer docMap and postings:
  indexing time = 120,860 ms
  querying time = 15,625 ms


> lazily create SegmentMergeInfo.docMap
> -------------------------------------
>
>          Key: LUCENE-454
>          URL: http://issues.apache.org/jira/browse/LUCENE-454
>      Project: Lucene - Java
>         Type: Improvement
>     Versions: CVS Nightly - Specify date in submission
>     Reporter: Yonik Seeley
>  Attachments: docMap.txt, docMap.txt
>
> Since creating the docMap is expensive, and it's only used during segment merging, not searching, defer creation until it is requested.
> SegmentMergeInfo is also used in MultiTermEnum, the term enumerator for a MultiReader.  TermEnum is used by queries such as PrefixQuery, RangeQuery, WildcardQuery, as well as RangeFilter, DateFilter, and sorting the first time (filling the FieldCache).
> Performance Results:
>   A simple single field index with 555,555 documents, and 1000 random deletions was queried 1000 times with a PrefixQuery matching a single document.
> Performance Before Patch:
>   indexing time = 121,656 ms
>   querying time = 58,812 ms
> Performance After Patch:
>   indexing time = 121,000 ms
>   querying time =         598 ms
> A 100 fold increase in query performance!
> All lucene unit tests pass.

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