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https://issues.apache.org/jira/browse/DERBY-3094?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12571751#action_12571751
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Bryan Pendleton commented on DERBY-3094:
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Thanks Army! That's a keen insight about the underlying issue, and
a great writeup and test case.
Here's yet another variant that's hard to explain: the first statement
works, the second is refused with error 42Y30:
select (a+b)+c, count(*) from t group by c, a+b;
select a+(b+c), count(*) from t group by c, a+b;
I'm not quite sure how to push this problem further. The only idea
I had was as follows: perhaps we could automatically and silently
pull up *every* column reference that is present in any GROUP BY
expression, and include that column as an extra column reference
at the end of the group by list. So we could rewrite the above queries,
for example, as:
select (a+b)+c, count(*) from t group by c, a+b, a, b;
select a+(b+c), count(*) from t group by c, a+b, a, b;
That might mean we'd always have "enough" column references
so that we could perform substitution on all the result columns
in the select list successfully.
Yet I'm nervous about this strategy; we wouldn't want these pulled
up columns to be used for the actual grouping (because it could
subdivide the actual groups further than the user intended), so we'd
have to mark these columns as "special columns to be used for
resolving column references, but not to be used for grouping."
I'll continue to think about it, but I'm increasingly tempted to
take your suggestion to be satisfied with the patch as is, and
file some of these other issues separately to be studied more
in the future. This is similar to the way that we marked DERBY-1624
as resolved, while shifting the unresolved portion out to DERBY-2457.
> Grouping of expressions causes NullPointerException
> ---------------------------------------------------
>
> Key: DERBY-3094
> URL: https://issues.apache.org/jira/browse/DERBY-3094
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.3.1.4
> Environment: Windows XP, Eclipse 3.2.2, java 1.5.0.11
> Reporter: Peter Balon
> Assignee: Bryan Pendleton
> Priority: Critical
> Attachments: d3094_followup.htm, modifyVisitorDoesntWork.diff,
> notes.html, twoPass.diff, TwoPassForHavingClauseAlso.diff,
> TwoPassVisitor.diff, TwoPassVisitorWithCommentsAndTests.diff
>
>
> Following steps to reproduce the bug:
> create table xx (a double, b double);
> insert into xx values (2, 3);
> select a, a*(b/100.000000), count(*) from xx group by a, a*(b/100.000000);
> Starting run
> select a, a*(b/100.000000), count(*) from xx
> group by a, a*(b/100.000000)
> Run successful
> SQL State = 38000 SQL Code = 20000 SQL Message = Bei der Auswertung eines
> Ausdrucks wurde die Ausnahme 'java.lang.NullPointerException' ausgelöst.
> Exception message = java.sql.SQLException: Bei der Auswertung eines Ausdrucks
> wurde die Ausnahme 'java.lang.NullPointerException' ausgelöst.
> Work around:
> select a, a*(b/100.000000), count(*) from xx group by a, b, a*(b/100.000000)
> Stack trace from application:
> java.sql.SQLException: Bei der Auswertung eines Ausdrucks wurde die Ausnahme
> 'java.lang.NullPointerException' ausgelöst.
> at
> org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
> at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Unknown Source)
> at org.apache.derby.impl.jdbc.Util.seeNextException(Unknown Source)
> at
> org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(Unknown
> Source)
> at
> org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(Unknown
> Source)
> at org.apache.derby.impl.jdbc.EmbedConnection.handleException(Unknown
> Source)
> at org.apache.derby.impl.jdbc.ConnectionChild.handleException(Unknown
> Source)
> at
> org.apache.derby.impl.jdbc.EmbedResultSet.closeOnTransactionError(Unknown
> Source)
> at org.apache.derby.impl.jdbc.EmbedResultSet.movePosition(Unknown
> Source)
> at org.apache.derby.impl.jdbc.EmbedResultSet.next(Unknown Source)
> at
> de.arcor.billy.report.views.designer.ReportViewerView.setInput(ReportViewerView.java:255)
> at
> de.arcor.billy.report.views.designer.ReportViewerView.createPartControl(ReportViewerView.java:113)
> at
> org.eclipse.ui.internal.ViewReference.createPartHelper(ViewReference.java:332)
> at
> org.eclipse.ui.internal.ViewReference.createPart(ViewReference.java:197)
> at
> org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:566)
> at org.eclipse.ui.internal.Perspective.showView(Perspective.java:1675)
> at
> org.eclipse.ui.internal.WorkbenchPage.busyShowView(WorkbenchPage.java:987)
> at
> org.eclipse.ui.internal.WorkbenchPage.access$13(WorkbenchPage.java:968)
> at org.eclipse.ui.internal.WorkbenchPage$13.run(WorkbenchPage.java:3514)
> at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:67)
> at
> org.eclipse.ui.internal.WorkbenchPage.showView(WorkbenchPage.java:3511)
> at
> de.arcor.billy.report.data.ReportDataAdvisor$2.perspectiveChanged(ReportDataAdvisor.java:268)
> at
> de.arcor.billy.system.actions.AbstractOpenPerspectiveActionDelegate$1.run(AbstractOpenPerspectiveActionDelegate.java:66)
> at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
> at
> org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:123)
> at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:3325)
> at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:2971)
> at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:1930)
> at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:1894)
> at
> org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:422)
> at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
> at de.arcor.billy.product.Billy.run(Billy.java:15)
> at
> org.eclipse.core.internal.runtime.PlatformActivator$1.run(PlatformActivator.java:78)
> at
> org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:92)
> at
> org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:68)
> at
> org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:400)
> at
> org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:177)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
> at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
> at java.lang.reflect.Method.invoke(Unknown Source)
> at org.eclipse.core.launcher.Main.invokeFramework(Main.java:336)
> at org.eclipse.core.launcher.Main.basicRun(Main.java:280)
> at org.eclipse.core.launcher.Main.run(Main.java:977)
> at org.eclipse.core.launcher.Main.main(Main.java:952)
> Caused by: java.sql.SQLException: Java-Ausnahme: ':
> java.lang.NullPointerException'.
> at
> org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
> at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Unknown Source)
> at org.apache.derby.impl.jdbc.Util.javaException(Unknown Source)
> at
> org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(Unknown
> Source)
> ... 42 more
> Caused by: java.lang.NullPointerException
> at
> org.apache.derby.exe.ac9b638174x0115x5f93x1332x0000046fd8a01b.e10(Unknown
> Source)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
> at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
> at java.lang.reflect.Method.invoke(Unknown Source)
> at org.apache.derby.impl.services.reflect.ReflectMethod.invoke(Unknown
> Source)
> at
> org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.doProjection(Unknown
> Source)
> at
> org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore(Unknown
> Source)
> at
> org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextRowFromSource(Unknown
> Source)
> at
> org.apache.derby.impl.sql.execute.ScrollInsensitiveResultSet.getNextRowCore(Unknown
> Source)
> at
> org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl.getNextRow(Unknown
> Source)
> ... 37 more
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