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https://issues.apache.org/jira/browse/LUCENE-4069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13285518#comment-13285518
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Mark Harwood commented on LUCENE-4069:
--------------------------------------
Thanks for the comment, Rob.
While the choice of Codec can be an anonymous inner class, resolving the choice
of PostingsFormat is trickier.
BloomFilterPostingsFormat is now intended to wrap any another choice of
PostingsFormat and Simon has suggested leaving the Bloom support purely
abstract.
However, as an end user if I want to use Bloom support on the standard Lucene
codec I would then have to write one of these:
{code:title=MyBloomFilteredLucene40Postings.java}
public class MyBloomFilteredLucene40Postingsextends
BloomFilteringPostingsFormatBase {
public MyBloomFilteredLucene40Postings() {
//declare my choice of PostingsFormat to be wrapped and provide a unique
name for this combo of Bloom-plus-delegate
super("myBL40", new Lucene40PostingsFormat());
}
}
{code}
The resulting index files are then named [segname]_myBL40.[filetypesuffix].
At read-time the "myBL40" bit of the filename is used to lookup via Service
Provider registrations the decoding class so
"com.xx.MyBloomFilteredLucene40Postings" would need adding to a
o.a.l.codecs.PostingsFormat file for the registration to work.
I imagine Bloom-plus-Lucene40Postings would be a common combo and if both are
in core it would be annoying to have to code support for this in each app or
for things like Luke to have to have classpaths redefined to access the
app-specific class that was created purely to bind this combo of core
components.
I think a better option might be to change the Bloom filtering base class to
record the choice of delegate PostingsFormat in it's own "blm" file at
write-time and instantiate the appropriate delegate instance at read-time using
the recorded name. The BloomFilteringBaseClass would need changing to a final
class rather than an abstract so that core Lucene could load it as the handler
for [segname]_BloomPosting.xxx files and it would then have to examine the
[segname].blm file to discover and instantiate the choice of delegate
PostingsFormat using the standard service registration mechanism. At write-time
clients would need to instantiate the BloomFilterPostingsFormat, passing a
choice of PostingsFormat delegate to the constructor. At read-time Lucene core
would invoke a zero-arg constructor.
I'll look into this as an approach.
> 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: BloomFilterCodec40.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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