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https://issues.apache.org/jira/browse/LUCENE-5476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13919380#comment-13919380
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Gilad Barkai commented on LUCENE-5476:
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Sorry if this was mentioned before and I missed it - how can sampling work
correctly (correctness of the end result) if it's done 'on the fly' ?
Beforehand, one cannot know the number of documents that would match the query,
as such, the sampling ratio is unknown, given that we can afford faceted search
over N documents only.
If the query yields 10K results and the sampling ration is 0.001 - would 10
documents make a good sample?
Same if the query yields 100M results - is 10K sample good enough? Is it
perhaps to much?
I find it hard to figure a pre-defined sampling ratio which would fit different
cases.
> Facet sampling
> --------------
>
> Key: LUCENE-5476
> URL: https://issues.apache.org/jira/browse/LUCENE-5476
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Rob Audenaerde
> Attachments: LUCENE-5476.patch, LUCENE-5476.patch, LUCENE-5476.patch,
> LUCENE-5476.patch, SamplingComparison_SamplingFacetsCollector.java,
> SamplingFacetsCollector.java
>
>
> 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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