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Posted to dev@lucene.apache.org by "Mark Harwood (JIRA)" <ji...@apache.org> on 2012/06/01 10:13:23 UTC
[jira] [Commented] (LUCENE-4069) Segment-level Bloom filters for a
2 x speed up on rare term searches
[ 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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