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https://issues.apache.org/jira/browse/HBASE-20928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16741782#comment-16741782
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Lars Hofhansl edited comment on HBASE-20928 at 1/14/19 6:15 AM:
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The cited article _explicitly_ states that
{{int mid = (low + high) >>> 1;}}
is OK and likely faster. I'm somewhat confused then about this change,
especially since said article is given as the reason.
[~stack]
I'm testing HBase 2 again HBase 1 right now and find that its scan performance
is 50% worse in many cases (with ROW_INDEX_V1 at least). Not saying this is
causing this, but it came up as a change in that code path)
was (Author: lhofhansl):
The cited article _explicitly_ states that
{{int mid = (low + high) >>> 1;}}
is OK and likely faster. I'm somewhat confused then about this change,
especially since said article is given as the reason.
> Rewrite calculation of midpoint in binarySearch functions to prevent overflow
> -----------------------------------------------------------------------------
>
> Key: HBASE-20928
> URL: https://issues.apache.org/jira/browse/HBASE-20928
> Project: HBase
> Issue Type: Bug
> Components: io
> Reporter: saurabh singh
> Assignee: saurabh singh
> Priority: Minor
> Fix For: 1.5.0, 2.2.0
>
> Attachments: HBASE-20928-addendum.patch,
> HBASE-20928-fix-binarySearch-v5.patch, HBASE-20928-fix-binarySearch-v5.patch
>
>
> There are couple of issues in the function:
> * {{>>>}} operator would mess the values if {{low}} + {{high}} end up being
> negative. This shouldn't happen but I don't see anything to prevent this from
> happening.
> * The code fails around boundary values of {{low}} and {{high}}. This is a
> well known binary search catch.
> [https://ai.googleblog.com/2006/06/extra-extra-read-all-about-it-nearly.html]
>
> Most of the code should already be covered by tests. I would have liked to
> add a test that actually fails without the fix but given these are private
> methods I am not sure on the best place to add the test. Suggestions?
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