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https://issues.apache.org/jira/browse/LUCENE-4069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13286616#comment-13286616
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Mark Harwood commented on LUCENE-4069:
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bq. I dont understand why this handles fields. Someone should just pick that
with perfieldpostingsformat.
That would be inefficient because your PFPF will see
BloomFilteringPostingsFormat(field1 + Lucene40) and
BloomFilteringPostingsFormat(field2 + Lucene40) as fundamentally different
PostingsFormat instances and consequently create multiple files named
differently because it assumes these instances may be capable of using
radically different file structures.
In reality, the choice of BloomFilter with field 1 or BloomFilter with field 2
or indeed no BloomFilter does not fundamentally alter the underlying delegate
PostingFormat's file format - it only adds a supplementary "blm" file on the
side with the field summaries. For this reason it is a mistake to configure
seperate BloomFilterPostingsFormat instances on a per-field basis if they can
share a common delegate.
> 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: BloomFilterPostings40.patch,
> MHBloomFilterOn3.6Branch.patch, PrimaryKey40PerformanceTestSrc.zip
>
>
> 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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