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https://issues.apache.org/jira/browse/SOLR-2564?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13045904#comment-13045904
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Martijn van Groningen commented on SOLR-2564:
---------------------------------------------
{quote}
I've been checking out the performance, and it generally seems fine. But of
course we normally short circuit based on comparators and often don't get
beyond that... so to exercise & isolate the rest of the code, I tried a
worst-case scenario where the short circuit wouldn't work (sort=docid desc) and
solr trunk with this patch is ~16% slower than without it. Any ideas what the
problem might be?
{quote}
What might be the problem is that the trunk is using (Grouping.java 589):
{code}
SearchGroup smallest = orderedGroups.pollLast();
{code}
Whilst the AbstractFirstPassGroupingCollector (line 217) is using:
{code}
final CollectedSearchGroup<GROUP_VALUE_TYPE> bottomGroup = orderedGroups.last();
orderedGroups.remove(bottomGroup);
{code}
The above also happen around line 271.
I haven't checked this out, but I think it is the most likely explanation
between those two implementations. Retrieving the bottom will be done in almost
all cases when the short circuit doesn't work
> Integrating grouping module into Solr 4.0
> -----------------------------------------
>
> Key: SOLR-2564
> URL: https://issues.apache.org/jira/browse/SOLR-2564
> Project: Solr
> Issue Type: Improvement
> Reporter: Martijn van Groningen
> Assignee: Martijn van Groningen
> Fix For: 4.0
>
> Attachments: LUCENE-2564.patch, SOLR-2564.patch, SOLR-2564.patch,
> SOLR-2564.patch, SOLR-2564.patch, SOLR-2564.patch
>
>
> Since work on grouping module is going well. I think it is time to wire this
> up in Solr.
> Besides the current grouping features Solr provides, Solr will then also
> support second pass caching and total count based on groups.
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