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https://issues.apache.org/jira/browse/DERBY-3219?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12595966#action_12595966
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Bryan Pendleton commented on DERBY-3219:
----------------------------------------
I kind of wandered around in the debugger for a while, and I noticed the
following:
1) The problem appears to occur when the "max" value in question is a SQLVarChar
whose value is "" (that is, a string of length 0).
2) The underlying exception which causes the problem is a EOFException
3) When reading a SQLVarchar whose value is "", we seem to normally
expect and handle an EOFException. See, in particular, this section of code
in SQLChar.readExternal:
} catch (EOFException eof) {
if (utflen != 0)
throw new EOFException();
// This is the case for a 0 length string.
// OR the string was originally streamed in
// which puts a 0 for utflen but no trailing
// E0,0,0 markers.
break readingLoop;
}
4) When the problem occurs, it seems that we don't get the expected
EOFException,
but rather we proceed a bit farther and then get the EOFException at an
unexpected point.
I'm wondering whether the problem is that the readExternal/writeExternal
implementation for SQL[var]char values of length 0 is flawed, because it
can only handle the case where the SQL[var]char value is at the *end* of
the buffer, but in the case of the MaxMinAggregator, the SQL[var]char value
is buried inside of a larger data structure (with boolean isNull and boolean
isMax)
bookends around the underlying value), and thus the EOFException occurs
unexpectedly.
> Group by query with many aggregate columns and case statements fails with:
> ERROR XSDA7: Restore of a serializable or SQLData object of class , attempted
> to read more data than was originally stored
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-3219
> URL: https://issues.apache.org/jira/browse/DERBY-3219
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.3.1.4
> Reporter: Stan Bradbury
> Attachments: pivotView.zip
>
>
> using the attached database (v10.3) - " select * from pivotview " fails with
> the stack trace below. A view (pivotview_ok) created on a subset of the
> columns in pivotview executes fine. Adding one column back into pivotview_ok
> causes failures most of the time. See attached for view definitions.
> 2007-11-21 00:58:49.421 GMT Thread[main,5,main] (XID = 2734422), (SESSIONID =
> 0), (DATABASE = pivotview), (DRDAID = null), Failed Statement is: select *
> from pivotview
> ERROR XSDA7: Restore of a serializable or SQLData object of class , attempted
> to read more data than was originally stored
> at org.apache.derby.iapi.error.StandardException.newException(Unknown
> Source)
> at
> org.apache.derby.impl.store.raw.data.StreamFileContainer.fetchNext(Unknown
> Source)
> at
> org.apache.derby.impl.store.raw.data.StreamFileContainerHandle.fetchNext(Unknown
> Source)
> at org.apache.derby.impl.store.access.sort.MergeScan.mergeARow(Unknown
> Source)
> at org.apache.derby.impl.store.access.sort.MergeScan.init(Unknown
> Source)
> at
> org.apache.derby.impl.store.access.sort.MergeSort.openSortScan(Unknown Source)
> at
> org.apache.derby.impl.store.access.RAMTransaction.openSortScan(Unknown Source)
> at
> org.apache.derby.impl.sql.execute.GroupedAggregateResultSet.loadSorter(Unknown
> Source)
> at
> org.apache.derby.impl.sql.execute.GroupedAggregateResultSet.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.EmbedStatement.execute(Unknown Source)
> at org.apache.derby.impl.jdbc.EmbedStatement.execute(Unknown Source)
> at org.apache.derby.impl.tools.ij.ij.executeImmediate(Unknown Source)
> at org.apache.derby.impl.tools.ij.utilMain.doCatch(Unknown Source)
> at org.apache.derby.impl.tools.ij.utilMain.runScriptGuts(Unknown Source)
> at org.apache.derby.impl.tools.ij.utilMain.go(Unknown Source)
> at org.apache.derby.impl.tools.ij.Main.go(Unknown Source)
> at org.apache.derby.impl.tools.ij.Main.mainCore(Unknown Source)
> at org.apache.derby.impl.tools.ij.Main14.main(Unknown Source)
> at org.apache.derby.tools.ij.main(Unknown Source)
> Caused by: java.io.EOFException
> at java.io.DataInputStream.readBoolean(DataInputStream.java:248)
> at
> org.apache.derby.impl.sql.execute.MaxMinAggregator.readExternal(Unknown
> Source)
> at
> org.apache.derby.iapi.services.io.FormatIdInputStream.readObject(Unknown
> Source)
> at org.apache.derby.iapi.types.UserType.readExternal(Unknown Source)
> ... 22 more
> ============= begin nested exception, level (1) ===========
> java.io.EOFException
> at java.io.DataInputStream.readBoolean(DataInputStream.java:248)
> at
> org.apache.derby.impl.sql.execute.MaxMinAggregator.readExternal(Unknown
> Source)
> at
> org.apache.derby.iapi.services.io.FormatIdInputStream.readObject(Unknown
> Source)
> at org.apache.derby.iapi.types.UserType.readExternal(Unknown Source)
> at
> org.apache.derby.impl.store.raw.data.StreamFileContainer.fetchNext(Unknown
> Source)
> at
> org.apache.derby.impl.store.raw.data.StreamFileContainerHandle.fetchNext(Unknown
> Source)
> at org.apache.derby.impl.store.access.sort.MergeScan.mergeARow(Unknown
> Source)
> at org.apache.derby.impl.store.access.sort.MergeScan.init(Unknown
> Source)
> at
> org.apache.derby.impl.store.access.sort.MergeSort.openSortScan(Unknown Source)
> at
> org.apache.derby.impl.store.access.RAMTransaction.openSortScan(Unknown Source)
> at
> org.apache.derby.impl.sql.execute.GroupedAggregateResultSet.loadSorter(Unknown
> Source)
> at
> org.apache.derby.impl.sql.execute.GroupedAggregateResultSet.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.EmbedStatement.execute(Unknown Source)
> at org.apache.derby.impl.jdbc.EmbedStatement.execute(Unknown Source)
> at org.apache.derby.impl.tools.ij.ij.executeImmediate(Unknown Source)
> at org.apache.derby.impl.tools.ij.utilMain.doCatch(Unknown Source)
> at org.apache.derby.impl.tools.ij.utilMain.runScriptGuts(Unknown Source)
> at org.apache.derby.impl.tools.ij.utilMain.go(Unknown Source)
> at org.apache.derby.impl.tools.ij.Main.go(Unknown Source)
> at org.apache.derby.impl.tools.ij.Main.mainCore(Unknown Source)
> at org.apache.derby.impl.tools.ij.Main14.main(Unknown Source)
> at org.apache.derby.tools.ij.main(Unknown Source)
> ============= end nested exception, level (1) ===========
> Cleanup action completed
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