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From "Rob Audenaerde (JIRA)" <>
Subject [jira] [Updated] (LUCENE-5476) Facet sampling
Date Tue, 04 Mar 2014 08:40:20 GMT


Rob Audenaerde updated LUCENE-5476:

    Attachment: LUCENE-5476.patch

New patch. 

My little benchmark results:

Exact  :176 ms
Sampled:36 ms

* I removed the {{SamplingParams}}. 
* I use random sampling in bins in the {{addDoc}}. This has almost no performance impact over
fix-internal samling when running with a sampleRatio of 0.001.
* Renamed the class to {{RandomSamplingFacetsCollector}}
* I decided to always add the first document of a segment. This counters the fact that randomindex
in the last bin is larger than the segment-size. Gives slightly better results. 

I do have some questions:

* Code style-wise: I see {{this.}} is sometimes used, and sometimes not. What do you prefer?
* It seems {{FixedBitSet}} contains a lot of empty space, as only 1 in 1000 hits are preserved.
I'm not that familiar with all the DocIdSet implementations, but maybe there are more suitable

> Facet sampling
> --------------
>                 Key: LUCENE-5476
>                 URL:
>             Project: Lucene - Core
>          Issue Type: Improvement
>            Reporter: Rob Audenaerde
>         Attachments: LUCENE-5476.patch, LUCENE-5476.patch, LUCENE-5476.patch,,
> With LUCENE-5339 facet sampling disappeared. 
> When trying to display facet counts on large datasets (>10M documents) counting facets
is rather expensive, as all the hits are collected and processed. 
> Sampling greatly reduced this and thus provided a nice speedup. Could it be brought back?

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