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https://issues.apache.org/jira/browse/LUCENE-4832?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aleksey Aleev updated LUCENE-4832:
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Attachment: LUCENE-4832.patch
Patch with proposed solution attached.
> Unbounded getTopGroups for ToParentBlockJoinCollector
> -----------------------------------------------------
>
> Key: LUCENE-4832
> URL: https://issues.apache.org/jira/browse/LUCENE-4832
> Project: Lucene - Core
> Issue Type: Improvement
> Components: modules/join
> Reporter: Aleksey Aleev
> Attachments: LUCENE-4832.patch
>
>
> _ToParentBlockJoinCollector#getTopGroups_ method takes several arguments:
> {code:java}
> public TopGroups<Integer> getTopGroups(ToParentBlockJoinQuery query,
> Sort withinGroupSort,
> int offset,
> int maxDocsPerGroup,
> int withinGroupOffset,
> boolean fillSortFields)
> {code}
> and one of them is {{maxDocsPerGroup}} which specifies upper bound of child
> documents number returned within each group.
> {{ToParentBlockJoinCollector}} collects and caches all child documents
> matched by given {{ToParentBlockJoinQuery}} in {{OneGroup}} objects during
> search so it is possible to create {{GroupDocs}} with all matched child
> documents instead of part of them bounded by {{maxDocsPerGroup}}.
> When you specify {{maxDocsPerGroup}} new queues(I mean
> {{TopScoreDocCollector}}/{{TopFieldCollector}}) will be created for each
> group with {{maxDocsPerGroup}} objects created within each queue which could
> lead to redundant memory allocation in case of child documents number within
> group is less than {{maxDocsPerGroup}}.
> I suppose that there are many cases where you need to get all child documents
> matched by query so it could be nice to have ability to get top groups with
> all matched child documents without unnecessary memory allocation.
> Possible solution is to pass negative {{maxDocsPerGroup}} in case when you
> need to get all matched child documents within each group and check
> {{maxDocsPerGroup}} value: if it is negative then we need to create queue
> with size of matched child documents number; otherwise create queue with size
> equals to {{maxDocsPerGroup}}.
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