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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4069) Segment-level Bloom filters for a 2 x speed up on rare term searches
Date Mon, 09 Jul 2012 17:58:34 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13409687#comment-13409687
] 

Michael McCandless commented on LUCENE-4069:
--------------------------------------------

bq. I added a 100mb start size for the BloomFilter for large-scale tests because without this
it gets saturated and there were occasional big spikes in batch times.

I wonder if somehow we can do a better job picking the right sized bit vector up front?  You
basically need to know up front how many unique terms will be in the given field for this
segment right?  This seems similar to LUCENE-4198, where we want to improve Codec API so it
has access to collection stats (like "number of unique terms in this field") up front.
                
> Segment-level Bloom filters for a 2 x speed up on rare term searches
> --------------------------------------------------------------------
>
>                 Key: LUCENE-4069
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4069
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: core/index
>    Affects Versions: 3.6, 4.0
>            Reporter: Mark Harwood
>            Priority: Minor
>             Fix For: 4.0, 3.6.1
>
>         Attachments: BloomFilterPostingsBranch4x.patch, LUCENE-4069-tryDeleteDocument.patch,
MHBloomFilterOn3.6Branch.patch, PKLookupUpdatePerfTest.java, PKLookupUpdatePerfTest.java,
PKLookupUpdatePerfTest.java, PrimaryKeyPerfTest40.java
>
>
> An addition to each segment which stores a Bloom filter for selected fields in order
to give fast-fail to term searches, helping avoid wasted disk access.
> Best suited for low-frequency fields e.g. primary keys on big indexes with many segments
but also speeds up general searching in my tests.
> Overview slideshow here: http://www.slideshare.net/MarkHarwood/lucene-bloomfilteredsegments
> Benchmarks based on Wikipedia content here: http://goo.gl/X7QqU
> Patch based on 3.6 codebase attached.
> There are no 3.6 API changes currently - to play just add a field with "_blm" on the
end of the name to invoke special indexing/querying capability. Clearly a new Field or schema
declaration(!) would need adding to APIs to configure the service properly.
> Also, a patch for Lucene4.0 codebase introducing a new PostingsFormat

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