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From "Mark Harwood (JIRA)" <>
Subject [jira] [Updated] (LUCENE-4069) Segment-level Bloom filters for a 2 x speed up on rare term searches
Date Fri, 08 Jun 2012 17:46:23 GMT


Mark Harwood updated LUCENE-4069:

    Attachment: BloomFilterPostingsBranch4x.patch

Updated as follows:
* Extracted Bloom filter functionality as new oal.util.FuzzySet class - the name is changed
because Bloom filtering is one application for a FuzzySet, fuzzy count distincts being another.
* BloomFilterPostingsFormat now take a factory that can tailor choice of BloomFilter per field
(bitset size/saturation settings and choice of hash algo). Provided a default factory implementation.
* All Unit tests pass now that I have a test PostingsFormat class that uses v small bitsets
where before the many-field unit tests would cause OOM. 

Will follow up with benchmarks when I have more time to run and document them. Initial results
from my large-scale tests on growing indexes show a nice flat line in the face of a growing
index whereas a non-Bloomed index saw-tooths upwards as segments grow/merge.
> Segment-level Bloom filters for a 2 x speed up on rare term searches
> --------------------------------------------------------------------
>                 Key: LUCENE-4069
>                 URL:
>             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, MHBloomFilterOn3.6Branch.patch
> 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:
> Benchmarks based on Wikipedia content here:
> 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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