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https://issues.apache.org/jira/browse/DERBY-6786?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14294886#comment-14294886
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Mamta A. Satoor commented on DERBY-6786:
----------------------------------------
I have done more debugging and found that the code in JoinNode:buildRCL() is
what is causing for us to run into NPE.
The code here checks if we already have built a ResultColumnList. If yes, then
we leave the routine with no other work.
/* NOTE - we only need to build this list if it does not
already
* exist. This can happen in the degenerate case of an insert
* select with a join expression in a derived table within the
select.
*/
if (getResultColumns() != null)
{
return;
}
If the ResultColumnList for JoinNode is not built yet, we go through the
LeftResultSet's result column list and make a copy of it, build virtual nodes
on top of them and then we do the same with RightResultSet's result column list
and then we append thecopy of the right resultcolumns to the copy of the left
result columns and use it as JoinNode's result column list.
In case of our INSERT case, as described earlier in this jira, we go through
two cycles of binds. Once for the SELECT inside the INSERT statement and then
for the bind of INSERT statement itself(which causes the SELECT to rebind
itself). In the first iteration of bind of the SELECT, the JoinNode.buildRCL
will find the resultcolumn list to be null and hence we build a result column
list using left resultset and right resultset. The second time when we come
again for the bind of the SELECT, we find that the result column list already
exist and hence we just return from this method. But I believe what is
happening is that the resultset list built in the first cycle ends up having
virtual nodes created on top of it and that causes it to loose its column id. I
removed the if condition from JoinNode.buildRCL and we do not run into NPE with
the test cases provided here. I am going to enable the junit test case
zztestDerby6786InsertIntoSelectCase3 and see if it runs successfully. I will
also run the test case added for DERBY-6788. If they both pass, I will run our
junit suite and derbyall suite to see how things go.
This if condition has been there from Derby 10.1 days(and that is why we see
the failures in 10.1 codeline as well). But my guess is that the reason we have
the if condition in JoinNode.buildRCL is to avoid recreating the result column
list. But it looks like, it should be ok to remove the if statement and let the
result column list to be built again during the second round of the bind of
SELECT in case of INSERT statement.
> 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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