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From "Bryan Pendleton (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3033) select query results in nullpointer exception in skipScan()
Date Wed, 26 Sep 2007 02:13:52 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3033?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12530347
] 

Bryan Pendleton commented on DERBY-3033:
----------------------------------------

This new failure is very interesting! My initial reaction is that it is the same problem,
with different symptoms. With the new (swapped tables) query:
 - we still go through exists flattening
 - we still go through transitive closure, and add a (erroneous) equijoin predicate
 - just before the crash, we trip the mysterious "if" statement in getColumnFromRow()
   and return a null column value 
 - applying the noClosureOfNotExists.diff patch removes the NPE and makes the
   query run correctly.
I'll keep stepping through the new NPE, as well as your modified query with the
previous query plan "shape", to continue to understand it better.


> select query results in nullpointer exception in skipScan()
> -----------------------------------------------------------
>
>                 Key: DERBY-3033
>                 URL: https://issues.apache.org/jira/browse/DERBY-3033
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.2.2.0
>         Environment: Windows XP, Java 5.0, JDBC, Derby 10.2.2.0
>            Reporter: Haolan Qin
>            Assignee: Bryan Pendleton
>         Attachments: bug4736.sql, d3033-sane-ij-session-10.3.1.5.txt, generatedActivation.txt,
noClosureOfNotExists.diff, query_plan.new, query_plan.old, queryPlanRS.txt, repro2.java, repro2.java,
repro3.java, test.rar, test.zip, viewer_10_1.zip
>
>
> The following error was repeatedly thrown when we tried to run a select query via JDBC.
Strangely, the exact same select query did not trigger any error when run from the command
line console. After we added an index, the error went away completely. 
> java.lang.NullPointerException
>  at org.apache.derby.impl.sql.execute.NoPutResultSetImpl.skipScan(Unknown Source)
>  at org.apache.derby.impl.sql.execute.TableScanResultSet.openCore(Unknown Source)
>  at org.apache.derby.impl.sql.execute.IndexRowToBaseRowResultSet.openCore(Unknown Source)
>  at org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.openCore(Unknown Source)
>  at org.apache.derby.impl.sql.execute.JoinResultSet.openRight(Unknown Source)
>  at org.apache.derby.impl.sql.execute.JoinResultSet.openCore(Unknown Source)
>  at org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.openCore(Unknown Source)
>  at org.apache.derby.impl.sql.execute.SortResultSet.openCore(Unknown Source)
>  at org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.openCore(Unknown Source)
>  at org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl.open(Unknown Source)
>  at org.apache.derby.impl.sql.GenericPreparedStatement.execute(Unknown Source)
>  at org.apache.derby.impl.jdbc.EmbedStatement.executeStatement(Unknown Source)
>  at org.apache.derby.impl.jdbc.EmbedPreparedStatement.executeStatement(Unknown Source)
>  at org.apache.derby.impl.jdbc.EmbedPreparedStatement.execute(Unknown Source)
>  at org.apache.derby.impl.drda.DRDAStatement.execute(Unknown Source)
>  at org.apache.derby.impl.drda.DRDAConnThread.processCommands(Unknown Source)
>  at org.apache.derby.impl.drda.DRDAConnThread.run(Unknown Source)

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