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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4069) Segment-level Bloom filters for a 2 x speed up on rare term searches
Date Fri, 25 May 2012 16:21:23 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13283574#comment-13283574
] 

Michael McCandless commented on LUCENE-4069:
--------------------------------------------

bq. I see a 35% improvement over standard Codecs on random lookups on a warmed index.

Impressive!  This is for primary key lookups?

It looks like the primary keys are GUID-like right?  (Ie randomly generated).  I wonder if
they had some structure instead (eg '%09d' % (id++)) how the results would look...

bq. I also notice that the PulsingCodec is no longer faster than standard Codec - is this
news to people as I thought it was supposed to be the way forward?

That's baffling to me: it should only save seeks vs Lucene40 codec, so on a cold index you
should see substantial gains, and on a warm index I'd still expect some gains.  Not sure what's
up...

bq. I can open a seperate JIRA issue for this 4.0 version of the code if that makes more sense.

I think it's fine to do it here?  Really 3.6.x is only for bug fixes now ... so I think we
should commit this to trunk.

I wonder if you can wrap any other PostingsFormat (ie instead of hard-coding to Lucene40PostingsFormat)?
 This way users can wrap any PF they have w/ the bloom filter...

Can you use FixedBitSet instead of OpenBitSet?  Or is there a reason to use OpenBitSet here...?
                
> 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
>            Reporter: Mark Harwood
>            Priority: Minor
>             Fix For: 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 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.

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