[jira] [Resolved] (LUCENE-6172) Improve the in-order / out-of-order collection decision process

["Adrien Grand (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/LUCENE-6172?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Adrien Grand resolved LUCENE-6172.
----------------------------------
    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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