[
https://issues.apache.org/jira/browse/LUCENE-5476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13917922#comment-13917922
]
Michael McCandless commented on LUCENE-5476:
--------------------------------------------
Patch looks good, and those are nice performance results!
But, can we please remove the SamplingParams class? There are only 2
params now; if we get up to 6 or 7 params then maybe we should switch
to a separate config class. I think one ctor taking only sampleRatio,
and then one other taking all params, is enough?
bq. When a segment has many docids but very few hits, they might be skipped
altogether. If this happens in many segments, the estimate gets more and more
off
bq. When a segment is small, there might be a few hits that are never touched
as the randomIndex in the 'bin-o-hits' is greater than the index of the hit.
I think these limitations are acceptable? In a large index, the
number of such "tiny" segments should be a tiny percentage of the doc
space; if not, something serious is wrong.
{quote}
bq. Another option, which would save the 2nd pass, would be to do the sampling
during Docs.addDoc.
I considered sampling on the 'addDocument' but I figured it would be
more expensive as then for each hit we need to do a random()
calculation.
{quote}
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?
> 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,
> 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?
--
This message was sent by Atlassian JIRA
(v6.2#6252)
---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org
For additional commands, e-mail: dev-h...@lucene.apache.org
