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Posted to dev@lucene.apache.org by "Shai Erera (JIRA)" <ji...@apache.org> on 2013/01/21 12:02:14 UTC
[jira] [Commented] (LUCENE-4610) Implement a NoParentsAccumulator
[ https://issues.apache.org/jira/browse/LUCENE-4610?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13558686#comment-13558686 ]
Shai Erera commented on LUCENE-4610:
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LUCENE-4600 added CountingFacetsCollector which supports OrdinalPolicy.NO_PARENTS (i.e. index only leaf nodes). Benchmark tests show that it performs better than when all parents are indexed (OrdinalPolicy.ALL_PARENTS), probably because less data is read from disk as well as less computation done during search.
We might therefore make NO_PARENTS the default OrdinalPolicy, and therefore need to address it for StandardFacetsAccumulator, perhaps in the form of a NoParentsAccumulator.
> Implement a NoParentsAccumulator
> --------------------------------
>
> Key: LUCENE-4610
> URL: https://issues.apache.org/jira/browse/LUCENE-4610
> Project: Lucene - Core
> Issue Type: New Feature
> Components: modules/facet
> Reporter: Shai Erera
> Attachments: LUCENE-4610.patch
>
>
> Mike experimented with encoding just the exact categories ordinals on LUCENE-4602, and I added OrdinalPolicy.NO_PARENTS, with a comment saying that this requires a special FacetsAccumulator.
> The idea is to write the exact categories only for each document, and then at search time count up the parents chain to compute requested facets (I say count, but it can be any weight).
> One limitation of such accumulator is that it cannot be used when e.g. a document is associated with two categories who share the same parent, because that may result in incorrect weights computed (e.g. a document might have several Authors, and so counting the Author facet may yield wrong counts). So it can be used only when the app knows it doesn't add such facets, or that it always asks to aggregate a 'root' that in its path this criteria doesn't hold (no categories share the same parent).
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