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https://issues.apache.org/jira/browse/LUCENE-6276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14955721#comment-14955721
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Paul Elschot commented on LUCENE-6276:
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We could take into account the different costs of advance() and nextDoc(), but
at another issue.
With cost() as an estimation of the number of matching documents, as it is now:
for conjunctions that could become: 2 * (minimum cost()) * (cost of advance),
and for disjunctions: (total cost()) * (cost of nextDoc).
ReqExclScorer could use the cost of advance in its matchCost already here, but
I have no idea which value to use.
> Add matchCost() api to TwoPhaseDocIdSetIterator
> -----------------------------------------------
>
> Key: LUCENE-6276
> URL: https://issues.apache.org/jira/browse/LUCENE-6276
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Robert Muir
> Attachments: LUCENE-6276-ExactPhraseOnly.patch,
> LUCENE-6276-NoSpans.patch, LUCENE-6276-NoSpans2.patch
>
>
> We could add a method like TwoPhaseDISI.matchCost() defined as something like
> estimate of nanoseconds or similar.
> ConjunctionScorer could use this method to sort its 'twoPhaseIterators' array
> so that cheaper ones are called first. Today it has no idea if one scorer is
> a simple phrase scorer on a short field vs another that might do some geo
> calculation or more expensive stuff.
> PhraseScorers could implement this based on index statistics (e.g.
> totalTermFreq/maxDoc)
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