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https://issues.apache.org/jira/browse/LUCENE-10374?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17475529#comment-17475529
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Greg Miller commented on LUCENE-10374:
--------------------------------------

OK, here's a thought: LUCENE-10350 actually does three things at once (or two 
depending on how you're counting).
 # Access the dense {{values}} array directly for counting instead of checking 
whether-or-not it's null every time it needs to increment a count.
 # Moves the check for whether-or-not {{liveDocs}} is null outside of the loop, 
and
 # Goes from using a for-loop to a while-loop since the docId is no longer 
needed inside the loop for checking against {{liveDocs}} if it's null (it 
retains the for-loop in the case that it needs to check {{liveDocs}}

I wonder if there's some optimization that's no longer taking place in some 
setups (JVM, hardware?) related to 2/3? Maybe there's some sort of loop 
optimization going on? The idea behind 1 seems so straight-forward that I 
really can't imagine it causing a regression, but who knows.

So I'm going to open new issues for 1 and 2/3 and try pushing those changes 
independently to see if we can narrow things down further.

> Track down the "browse" taxonomy faceting qps regression
> --------------------------------------------------------
>
>                 Key: LUCENE-10374
>                 URL: https://issues.apache.org/jira/browse/LUCENE-10374
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: modules/facet
>            Reporter: Greg Miller
>            Priority: Major
>
> We need to track down the source of the regression observed here: 
> [https://home.apache.org/~mikemccand/lucenebench/2022.01.10.18.03.12.html.]
> Some details on the regression hunting are in 
> [https://github.com/apache/lucene/pull/597.] 



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