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https://issues.apache.org/jira/browse/DERBY-3479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12575474#action_12575474
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Knut Anders Hatlen commented on DERBY-3479:
-------------------------------------------

The buffer manager from DERBY-2911 delegates more of the page cleaning to the 
background thread. This could perhaps explain why the row count statistics are 
different. Where the old buffer manager cleans a page synchronously in the user 
thread and thereby updates the statistics, the new buffer manager may have 
given the page to the background thread and therefore doesn't update the 
statistics until a moment later.

Compressing the tables sounds like a good idea, but it does indeed look strange 
with the extra page. Aren't all of these tables so small that they should fit 
on a single page?

> Changed/unexpected query plan when running test 'lang/predicatePushdown.sql'
> ----------------------------------------------------------------------------
>
>                 Key: DERBY-3479
>                 URL: https://issues.apache.org/jira/browse/DERBY-3479
>             Project: Derby
>          Issue Type: Bug
>          Components: Regression Test Failure
>    Affects Versions: 10.4.0.0
>         Environment: OS: Solaris 10 6/06 s10x_u2wos_09a X86 64bits - SunOS 
> 5.10 Generic_118855-14
> JVM: Sun Microsystems Inc., java version "1.6.0_04", Java(TM) SE Runtime 
> Environment (build 1.6.0_04-b12), Java HotSpot(TM) Client VM (build 10.0-b19, 
> mixed mode)
>            Reporter: Ole Solberg
>         Attachments: d3479_1.diff
>
>
> Seen in tinderbox since r631930.
> See e.g. 
> http://dbtg.thresher.com/derby/test/tinderbox_trunk16/jvm1.6/testing/testlog/SunOS-5.10_i86pc-i386/631932-derbyall_diff.txt
>  :
> *** Start: predicatePushdown jdk1.6.0_04 derbyall:derbylang 2008-02-28 
> 14:02:49 ***
> 9285 del
> <             Rows seen from the left = 20
> 9285a9285
> >             Rows seen from the left = 10
> 9297 del
> <                     Rows seen from the right = 20
> 9297a9297
> >                     Rows seen from the right = 10
> 9299 del
> <                     Rows returned = 20
> 9299a9299
> >                     Rows returned = 10
> .
> .
> .

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