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https://issues.apache.org/jira/browse/LUCENE-6172?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Adrien Grand resolved LUCENE-6172.
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Resolution: Won't Fix
Closed in favor of LUCENE-6179
> Improve the in-order / out-of-order collection decision process
> ---------------------------------------------------------------
>
> Key: LUCENE-6172
> URL: https://issues.apache.org/jira/browse/LUCENE-6172
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Adrien Grand
> Assignee: Adrien Grand
> Priority: Minor
> Fix For: 5.0, Trunk
>
> Attachments: LUCENE-6172.patch
>
>
> Today the logic is the following:
> - IndexSearcher looks if the weight can score out-of-order
> - Depending on the value it creates the appropriate top docs/field collector
> I think this has several issues:
> - Only IndexSearcher can actually make the decision correctly, and it only
> works for top docs/field collectors. If you want to make a multi collector in
> order to have both facets and top docs, then you're clueless about whether
> you should create a top docs collector that supports out-of-order collection
> - It is quite fragile: you need to make sure that
> Weight.scoresDocsOutOfOrder and Weight.bulkScorer agree on when they can
> score out-of-order. Some queries like BooleanQuery duplicate the logic and
> other queries like FilteredQuery just always return true to avoid complexity.
> This is inefficient as this means that IndexSearcher will create a collector
> that supports out-of-order collection while the common case actually scores
> documents in order (leap frog between the query and the filter).
> Instead I would like to take advantage of the new collection API to make
> out-of-order scoring an implementation detail of the bulk scorers. My current
> idea is as follows:
> - remove Weight.scoresDocsOutOfOrder
> - change Collector.getLeafCollector(LeafReaderContext) to
> Collector.getLeafCollector(LeafReaderContext, boolean canScoreOutOfOrder)
> This new boolean in Collector.getLeafCollector tells the collector that the
> scorer supports out-of-order scoring. So by returning a leaf collector that
> supports out-of-order collection, things will be faster.
> The new logic would be the following. First Weights cannot tell whether they
> support out-of-order scoring or not. However when a weight knows it supports
> out-of-order scoring, it will pass canScoreOutOfOrder=true when getting the
> leaf collector. If the returned collector accepts documents out of order,
> then the weight will return an out-of order scorer. Otherwise, an in-order
> scorer is returned.
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