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https://issues.apache.org/jira/browse/DERBY-6786?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14265822#comment-14265822
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Mamta A. Satoor edited comment on DERBY-6786 at 1/6/15 8:17 AM:
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While looking at the issue, I found that the queries from repro sql do not
result into NPE if the data in the tables is different.
create table k1 (k varchar(64), s decimal);
create table k2 (k varchar(64), s decimal);
create table t (s decimal);
insert into k1 values ('110007', 224);
insert into k2 values ('110007', 361);
Note that both the tables above have same value for column k and thus join will
actually result in matching rows.
Now for all the 4 queries provided in repro case by Johannes will actually find
a matching row and for such a data, there is no NPE.
In the case where no matching row is found(which is the case with the data set
provided in the repro case by Johannes), issue might be that Derby is not
equipped to handle empty resultset for the 2 queries provided in the repro.
was (Author: mamtas):
While looking at the issue, I found that the queries from repro sql do not
result into NPE if the data in the tables is different.
create table k1 (k varchar(64), s decimal);
create table k2 (k varchar(64), s decimal);
create table t (s decimal);
insert into k1 values ('110007', 224);
insert into k2 values ('110007', 361);
Note that both the tables above has same value for column k and thus join will
actually result in matching rows.
Now for all the 4 queries provided in repro case by Johannes will actually find
a matching row and for such a data, there is no NPE. In the case where no
matching row is found, issue might be that Derby is not equipped to handle such
a case for the 2 queries provided in the repro.
> 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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