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From "Rob Audenaerde (JIRA)" <>
Subject [jira] [Commented] (LUCENE-5476) Facet sampling
Date Mon, 03 Mar 2014 12:44:20 GMT


Rob Audenaerde commented on LUCENE-5476:

Quick update:

I implemented the single pass on the 'addDoc' method using a fixed interval (which should
be the fastest implementation I guess)

Exact: 180ms
Single Pass (no-clone) Fixed Interval: 38ms. 

This is a 4.5x speed-up. 

I will compare this later on with a single pass random indexed approach. 

Hmm, I don't think the single-pass option would require
xorshift.nextInt() on every call? Couldn't you keep a countInBin
field in your SampledDocs, increment it on each Docs.addDoc, and when
it's == randomIndex, add to the sampled bits and then pick a new
randomIndex? This should save a 2nd pass iteration?

Yes I thought of this too. I will update this. I think I prefer the single pass option myself,
as I do not need the original bitset and the faster option. 

> Facet sampling
> --------------
>                 Key: LUCENE-5476
>                 URL:
>             Project: Lucene - Core
>          Issue Type: Improvement
>            Reporter: Rob Audenaerde
>         Attachments: 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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