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From "Michael McCandless (JIRA)" <>
Subject [jira] [Commented] (LUCENE-4069) Segment-level Bloom filters for a 2 x speed up on rare term searches
Date Wed, 20 Jun 2012 11:18:43 GMT


Michael McCandless commented on LUCENE-4069:

Hmm somehow I messed up when testing the bloom postings format: all of my on-disk bloom bits
sets are 8 MB, regardless of the size of the segment... so something is wrong (I would expect
segments w/ more terms to have a larger bit set...).  This is what I did for the codec:
    final Codec codec = new Lucene40Codec() {
      public PostingsFormat getPostingsFormatForField(String field) {
        final String pfName = field.equals("id") ? idFieldPostingsFormat : defaultPostingsFormat;
        if (pfName.equals("Bloom")) {
          return new BloomFilteringPostingsFormat(PostingsFormat.forName("Lucene40"),
                                                  new BloomFilterFactory() {
                                                    public FuzzySet getSetForField(FieldInfo
info) {    
                                                      return FuzzySet.createSetBasedOnMaxMemory(100*1024*1024,
new MurmurHash2());
        } else {
          return PostingsFormat.forName(pfName);

I thought that would use plenty of RAM (100 MB), and then downsize to the appropriately sized
bit set (~10% saturation) when writing ... but somehow it didn't.
> 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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