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https://issues.apache.org/jira/browse/LUCENE-4069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13397425#comment-13397425
]
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:
{noformat}
final Codec codec = new Lucene40Codec() {
@Override
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() {
@Override
public FuzzySet
getSetForField(FieldInfo info) {
return
FuzzySet.createSetBasedOnMaxMemory(100*1024*1024, new MurmurHash2());
}
});
} else {
return PostingsFormat.forName(pfName);
}
}
};
{noformat}
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: 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,
> MHBloomFilterOn3.6Branch.patch, 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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