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https://issues.apache.org/jira/browse/DERBY-3819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12620554#action_12620554
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Kristian Waagan commented on DERBY-3819:
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A B wrote:
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But that assumption was wrong, esp. in the case of refSize, which varies from
machine to machine (esp. 32-bit vs 64 bit).
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It is my understanding that refSize will be either 4 or 8, depending on whether
the VM is 32-bit or 64-bit.
Assuming 'sun.arch.data.model' can only be 32 or 64, this is enforced by the
two first steps in the algorithm:
a) 'sun.arch.data.model' / 8
b) 'os.arch'; hardcoded values (4 and 8) if the arch string is known
Step c), which is the original heuristic, can result in values from 4 and up.
On my machine it calculated refSize to be -26, but no values smaller than 4 are
returned.
According to Knut Anders (see DERBY-3794), there are other variables used that
make the estimates more or less wrong, but they are either constants or based
on refSize and we shouldn't see "random values" as long as refSize is stable.
The refSize calculation changes are documented in DERBY-3731.
> 'Expected Table Scan ResultSet for T3' in
> 'test_predicatePushdown(....PredicatePushdownTest)' since 670215 2008-06-21
> 18:01:08 MEST
> -----------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-3819
> URL: https://issues.apache.org/jira/browse/DERBY-3819
> Project: Derby
> Issue Type: Bug
> Components: Regression Test Failure
> Affects Versions: 10.5.0.0
> Environment: OS: Solaris 10 5/08 s10x_u5wos_10 X86 64bits - SunOS
> 5.10 Generic_127128-11 (sol)
> JVM: Sun Microsystems Inc.
> java version "1.6.0_06"
> Java(TM) SE Runtime Environment (build 1.6.0_06-b02)
> Java HotSpot(TM) 64-Bit Server VM (build 10.0-b22 mixed mode 64-bit)
> Reporter: Ole Solberg
> Assignee: Kathey Marsden
> Attachments: new_plan.txt, old_plan.txt
>
>
> 'test_predicatePushdown(org.apache.derbyTesting.functionTests.tests.lang.PredicatePushdownTest)junit.framework.AssertionFailedError:
> Expected Table Scan ResultSet for T3' since 670215 2008-06-21 18:01:08 MEST
> http://dbtg.thresher.com/derby/test/Daily/UpdateInfo/670215.txt
> The failure is seen on SunOS 5.10 / Sun Jvm 1.6.0.
> See e.g.
> http://dbtg.thresher.com/derby/test/Daily/jvm1.6/testing/testlog/sol/682186-suitesAll_diff.txt
> The test (suites.All) is run with '-XX:-UseThreadPriorities
> -XX:MaxPermSize=128M -Xmx256M -d64'.
> When run with '-XX:MaxPermSize=128M -Xmx256M' as is used for the other
> platforms in this set of tests we do not see a failure.
> The failure was also seen on Solaris Express Community Edition snv_86 X86bits
> - SunOS 5.11 snv_86 (solN+1) between 670215 and 676638.
> (Run w/ -XX:-UseThreadPriorities -XX:MaxPermSize=128M -Xmx256M -d32)
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