[jira] Updated: (DERBY-1902) Intermittent failures in predicatePushdown.sql

["Mike Matrigali (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/DERBY-1902?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Mike Matrigali updated DERBY-1902:
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I am ok with upping the maxMemory to get this test to be reproducible on multiple systems.

I also wonder if it would be ok to look at upping the default for this in the whole system.  That default was chosen
a number of years ago.  Derby query processing performs WAY better whenever it can use hash join vs. other
types of join.  These defaults are hard to choose as there will always be someone that the default is not right for.
I would argue we should only change the default in a major new release, and never backport the change to 
an already released version.  

This is a standard memory for performance tradeoff.  The memory usage is only for the time it takes to process
the query, and is then released. 

I am not sure the right number, thinking about proposing 10meg vs. 1 meg.   The default buffer cache size use
to be under 100 pages and has since been updated to be 1000 pages.  should this be a hard vs. soft upgrade
thing? 

This should probably be handled under a separate jira.  Along with this someone should look and see if this
number should be coordinated with any other similar number in query processing.  

> Intermittent failures in predicatePushdown.sql
> ----------------------------------------------
>
>                 Key: DERBY-1902
>                 URL: https://issues.apache.org/jira/browse/DERBY-1902
>             Project: Derby
>          Issue Type: Bug
>          Components: Regression Test Failure, SQL, Test
>    Affects Versions: 10.3.1.4
>         Environment: Seen on both Solaris 10 and Linux on 2-CPU Opteron boxes, disk cache off
>            Reporter: Øystein Grøvlen
>         Attachments: derbylang.zip
>
>
> For the last week, there have been intermittent failures in the night test in lang/predicatePushdown.sql.  There is a plan diff which starts as follows:
> ********* Diff file derbyall/derbylang/predicatePushdown.diff
> *** Start: predicatePushdown jdk1.5.0_07 derbyall:derbylang 2006-09-29 00:39:36 ***
> 4593 del
> < 			Hash Join ResultSet:
> 4593a4593
> > 			Nested Loop Join ResultSet:
> I did not find any changes that seem relevant before the first failing night test.
> This test has not failed in the tinderbox test which runs on a computer with the disk cache on.  For both computers where the failure is seen, the disk cache has been turned off.  Hence, it may be that another plan is picked because of slower I/O.

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