[jira] [Commented] (LUCENE-4607) Add estimateDocCount to DocIdSetIterator

["Uwe Schindler (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-4607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13527982#comment-13527982 ] 

Uwe Schindler commented on LUCENE-4607:
---------------------------------------

Nice idea! At least the FilteredQuery code looks fine to me. I agree, the Bits interface and FixedBitSet has a costly cardinality (Bits does not have it at all...), so we should think about that. As far as I see it returns maxDoc as cost.
                
> Add estimateDocCount to DocIdSetIterator
> ----------------------------------------
>
>                 Key: LUCENE-4607
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4607
>             Project: Lucene - Core
>          Issue Type: Bug
>          Components: core/search
>    Affects Versions: 4.0
>            Reporter: Simon Willnauer
>             Fix For: 4.1, 5.0
>
>         Attachments: LUCENE-4607.patch
>
>
> this is essentially a spinnoff from LUCENE-4236
> We currently have no way to make any decsision on how costly a DISI is neither when we apply filters nor when we build conjunctions in BQ. Yet we have most of the information already and can easily expose them via a cost API such that BS and FilteredQuery can apply optimizations on per segment basis.

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