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https://issues.apache.org/jira/browse/DERBY-3094?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12570783#action_12570783
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A B commented on DERBY-3094:
----------------------------
Thank you for the updated patch, Bryan. Is there a more detailed writeup
forthcoming for this change, or are the code comments the extent of it?
The reason I ask is that, after reading the code comments and the comments in
this issue, I can't quite see the correlation between the patch and the NPE
that it fixes. That is, it's clear that the patch fixes the issue, but I think
I'm missing the details on _why_. The code comments say:
// then we don't want the replacement of the
// simple column reference C1 to affect the
// compound expression C1 * (C2 / 100).
but it's not clear to me how replacement of the simple column reference can
negatively affect the compound expressions. Is it an issue of VCN's pointing
to the wrong place? If so, any idea as to why that happens? Similarly, in an
earlier comment you noted:
> I think it's instructive to note that, with this patch applied, the
> following statement gets "b" and "a" backward:
> ij> select b, a, count(*) from xx group by b, a;
> B |A |3
> ---------------------------------------------------------
> 2.0 |3.0 |1
Is it possible to say what it is about processing simple column references
_after_ compound expressions that fixes this problem?
Apologies if I'm missing something obvious. I'm not by any means opposed to
the patch, I'm just hoping to gain an understanding about why it resolves the
discussion/issues raised thus far for this issue...
And thanks for your continued diligence with this one, Bryan.
> 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: modifyVisitorDoesntWork.diff, twoPass.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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