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From "Manfred Steinsiek (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6786) NullPointerException in INSERT INTO statement with multiple subselects
Date Thu, 08 Jan 2015 09:08:35 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6786?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14269019#comment-14269019
] 

Manfred Steinsiek commented on DERBY-6786:
------------------------------------------

Two additional observations:

1) The bug seems to be very old: It can be reproduced in Derby 10.1.1 (dating from August
2005).

2) There is an even simpler statement producing the same kind of NullPointerException
...
Caused by: java.lang.NullPointerException
	at org.apache.derby.exe.acf81e0010x014axc8afx79cbx00000031dbd00.e2(GC.java:29)
	at org.apache.derby.impl.services.reflect.DirectCall.invoke(ReflectGeneratedClass.java:105)
	at org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore(ProjectRestrictResultSet.java:302)
...

namely:

insert into t
	select erg.* from (
		select d2.s from k1
			left join (select k,s from k2) as d2 on k1.k=d2.k
		) as erg
	where s > 10

thus reducing the complexity of the example given above (which is already extraordinarily
simple) by one subselect.



> NullPointerException in INSERT INTO statement with multiple subselects
> ----------------------------------------------------------------------
>
>                 Key: DERBY-6786
>                 URL: https://issues.apache.org/jira/browse/DERBY-6786
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.2.2.0, 10.5.1.1, 10.8.2.2, 10.9.1.0, 10.10.1.1, 10.11.1.1
>         Environment: not relevant, but tested under Windows 7 32bit, Windows Server 2008
64bit, Java 6 and Java 7.
>            Reporter: Johannes Stadler
>              Labels: NullPointerException
>         Attachments: acaaeec04ex014axaa2ex076bx000000c72a081.java, repro.sql
>
>
> Hello,
> I'm getting this wrapped NullPointerException when I try to execute an INSERT INTO SQL
statement:
> java.sql.SQLException: The exception 'java.lang.NullPointerException' was thrown while
evaluating an expression.
> 	at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(SQLExceptionFactory40.java:101)
> 	at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Util.java:148)
> 	at org.apache.derby.impl.jdbc.Util.seeNextException(Util.java:349)
> 	at org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(TransactionResourceImpl.java:431)
> 	at org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(TransactionResourceImpl.java:353)
> 	at org.apache.derby.impl.jdbc.EmbedConnection.handleException(EmbedConnection.java:2400)
> 	at org.apache.derby.impl.jdbc.ConnectionChild.handleException(ConnectionChild.java:85)
> 	at org.apache.derby.impl.jdbc.EmbedStatement.executeStatement(EmbedStatement.java:1437)
> 	at org.apache.derby.impl.jdbc.EmbedStatement.execute(EmbedStatement.java:711)
> 	at org.apache.derby.impl.jdbc.EmbedStatement.executeLargeUpdate(EmbedStatement.java:190)
> 	at org.apache.derby.impl.jdbc.EmbedStatement.executeUpdate(EmbedStatement.java:179)
> 	at de.foconis.dakobp.unittests.div.TestMain.testNullpointer(TestMain.java:49)
> 	at de.foconis.dakobp.unittests.div.TestMain.main(TestMain.java:28)
> Caused by: java.sql.SQLException: The exception 'java.lang.NullPointerException' was
thrown while evaluating an expression.
> 	at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(SQLExceptionFactory.java:42)
> 	at org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(SQLExceptionFactory40.java:125)
> 	at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(SQLExceptionFactory40.java:71)
> 	... 12 more
> Caused by: java.sql.SQLException: Java exception: ': java.lang.NullPointerException'.
> 	at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(SQLExceptionFactory.java:42)
> 	at org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(SQLExceptionFactory40.java:125)
> 	at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(SQLExceptionFactory40.java:71)
> 	at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Util.java:148)
> 	at org.apache.derby.impl.jdbc.Util.javaException(Util.java:370)
> 	at org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(TransactionResourceImpl.java:436)
> 	... 10 more
> Caused by: java.lang.NullPointerException
> 	at org.apache.derby.exe.acf81e0010x014axa9c2x46e6x000000c6dc781.e2(Unknown Source)
> 	at org.apache.derby.impl.services.reflect.DirectCall.invoke(ReflectGeneratedClass.java:105)
> 	at org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore(ProjectRestrictResultSet.java:275)
> 	at org.apache.derby.impl.sql.execute.ProjectRestrictResultSet.getNextRowCore(ProjectRestrictResultSet.java:263)
> 	at org.apache.derby.impl.sql.execute.DMLWriteResultSet.getNextRowCore(DMLWriteResultSet.java:127)
> 	at org.apache.derby.impl.sql.execute.InsertResultSet.open(InsertResultSet.java:519)
> 	at org.apache.derby.impl.sql.GenericPreparedStatement.executeStmt(GenericPreparedStatement.java:461)
> 	at org.apache.derby.impl.sql.GenericPreparedStatement.execute(GenericPreparedStatement.java:340)
> 	at org.apache.derby.impl.jdbc.EmbedStatement.executeStatement(EmbedStatement.java:1344)
> 	... 5 more
> Most likely this bug has already been reported as DERBY-5041, which has already been
closed (although I don't use a GROUP BY clause).
> The original statement is quite complex and partially generated, but the error can be
reproduced easily, using a statement as simple as this:
> insert into t
>  select erg.* from (
>   select d1.s from (select k,s from k1) as d1
>    right join (select k,s from k2) as d2 on d1.k = d2.k
>   ) as erg
>  where s > 10
> I will attach the file "repro.sql", containing all SQL statements required to reproduce
it (including the CREATE TABLEs).
> These are my investigation results:
> Conditions
> -------------
> 1. the outermost statement must NOT be a SELECT (e. g. INSERT)
> 2. there has to be a outer join in the subselect, where at least one dataset has no join
partner
> 3. an outer SELECT must have a restriction (WHERE clause) and access a column from the
table, that did not have a join partner
> Error state
> -------------
> The NullPointer occurs inside a generated class. So i enabled the Debug Option "DumpClassFile",
to get the generated class file (the decompiled java class file will also be appended).
> The method "e2", stated in the StackTrace, performs the restrction "where s > 10".
Therefore it calls getColumnFromRow() with its resultSetNumber.
> This is where the error occurs: there is no "current row" available. Precisely, the "row"
property of the activation class at the specified index (which is the resultSetNumber=3 in
this example) is not set.
> It gets a bit complicated now, I will try to explain it, starting with the generated
resultset hierarchy.
> This tree of resultset implementations is generated to perform the query:
> Implementation				resultSetNumber
> -------------------				---------------------
> InsertResultSet			-> none
>  ProjectRestrictResultSet		-> 5
>   ProjectRestrictResultSet	-> 4
>    HashLeftOuterJoinResultSet	-> 0
>     TableScanResultSet		-> 1
>     HashTableResultSet		-> 3
>      TableScanResultSet		-> 2
> The HashTableResultSet, which got the resultSetNumber 3 doesn't set a current row, because
there is no join partner (still everything correct). But the ProjectRestrictResultSet on position
4 uses the restriction method ("e2"), which accesses a column on resultSetNumber 3 -> error.
> As far as I can tell, a restriction must never relate to the source of an outer join
ResultSet. The numeration error does not occur, if the outermost statement is a SELECT and
the numeration is generated top-down.
> Unfortunately I couldn't find an easy solution for this problem. In my case, this is
a critical bug, because changing the query as workaround is difficult, since parts of it are
generated. Please note, that this error is not dependent on any environment settings or platform
and occured with all of the abolve mentioned versions. I didn't test the versions from 10.6
to 10.7, but probably those are also affected.
> If you require any further information, please let me know. I'm able to perform a build,
so I wouldn't need a full version, a patch would be sufficient.



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