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Date: Fri, 1 Jun 2012 08:13:23 +0000 (UTC)
From: "Mark Harwood (JIRA)" <jira@apache.org>
To: dev@lucene.apache.org
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Subject: [jira] [Commented] (LUCENE-4069) Segment-level Bloom filters for a
 2 x speed up on rare term searches
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    [ https://issues.apache.org/jira/browse/LUCENE-4069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13287258#comment-13287258 ] 

Mark Harwood commented on LUCENE-4069:
--------------------------------------

I've thought some more about option 2 (PerFieldPF reusing wrapped PFs) and it looks to get very ugly very quickly.
There's only so much PerFieldPF can do to rationalize a random jumble of PF instances presented to it by clients. I think the right place to draw the line is Lucene-4093 i.e. a simple .equals() comparison on top-level PFs to eliminate any duplicates. Any other approach that also tries to de-dup nested PFs looks to be adding a lot of complexity, especially when you consider what that does to the model of read-time object instantiation. This would be significant added complexity to solve a problem you have already suggested is insignificant (i.e. too many files doesn't really matter when using CFS).

I can remove the per-field stuff from BloomPF if you want but I imagine I will routinely subclass it to add this optimisation back in to my apps.


> 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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