NullPointerException when re-evaluating generated column during ON DELETE SET NULL referential action

• Key: DERBY-3964
• Type: Bug
• Status: Resolved
• Resolution: Fixed
• Priority: Major
• Assignee: Rick Hillegas
• Reporter: Dag H. Wanvik
• Component/s: SQL
• Affects Version/s: 10.5.1.1
• Fix Version/s: 10.5.1.1

Description

Cf repro RegenerateAfterOnDeleteSetNullError.java enclosed.

1) test_1(org.apache.derbyTesting.functionTests.tests.lang.RegenerateAfterOnDeleteSetNullError)java.sql.SQLException: The exception 'java.lang.NullPointerException' was thrown while evaluating an expression.
at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(SQLExceptionFactory40.java:95)
at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Util.java:87)
at org.apache.derby.impl.jdbc.Util.seeNextException(Util.java:223)
at org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(TransactionResourceImpl.java:398)
at org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(TransactionResourceImpl.java:346)
at org.apache.derby.impl.jdbc.EmbedConnection.handleException(EmbedConnection.java:2201)
at org.apache.derby.impl.jdbc.ConnectionChild.handleException(ConnectionChild.java:81)
at org.apache.derby.impl.jdbc.EmbedStatement.executeStatement(EmbedStatement.java:1323)
at org.apache.derby.impl.jdbc.EmbedStatement.execute(EmbedStatement.java:625)
at org.apache.derby.impl.jdbc.EmbedStatement.executeUpdate(EmbedStatement.java:175)
at org.apache.derbyTesting.functionTests.tests.lang.RegenerateAfterOnDeleteSetNullError.test_1(RegenerateAfterOnDeleteSetNullError.java:60)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at org.apache.derbyTesting.junit.BaseTestCase.runBare(BaseTestCase.java:105)
at junit.extensions.TestDecorator.basicRun(TestDecorator.java:24)
at junit.extensions.TestSetup$1.protect(TestSetup.java:21)
at junit.extensions.TestSetup.run(TestSetup.java:25)
at org.apache.derbyTesting.junit.BaseTestSetup.run(BaseTestSetup.java:57)
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:45)
at org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(SQLExceptionFactory40.java:119)
at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(SQLExceptionFactory40.java:70)
... 31 more
Caused by: java.sql.SQLException: Java exception: ': java.lang.NullPointerException'.
at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(SQLExceptionFactory.java:45)
at org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(SQLExceptionFactory40.java:119)
at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(SQLExceptionFactory40.java:70)
at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Util.java:87)
at org.apache.derby.impl.jdbc.Util.javaException(Util.java:244)
at org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(TransactionResourceImpl.java:403)
... 29 more
Caused by: java.lang.NullPointerException
at org.apache.derby.impl.sql.execute.BaseActivation.getColumnFromRow(BaseActivation.java:1451)
at org.apache.derby.exe.ac30fbc0bbx011dxd4a8x4baexffffd28a99d54.e5(Unknown Source)
at org.apache.derby.impl.services.reflect.DirectCall.invoke(ReflectGeneratedClass.java:149)
at org.apache.derby.impl.sql.execute.NoRowsResultSetImpl.evaluateGenerationClauses(NoRowsResultSetImpl.java:623)
at org.apache.derby.impl.sql.execute.UpdateResultSet.collectAffectedRows(UpdateResultSet.java:451)
at org.apache.derby.impl.sql.execute.DeleteCascadeResultSet.collectAffectedRows(DeleteCascadeResultSet.java:195)
at org.apache.derby.impl.sql.execute.DeleteCascadeResultSet.open(DeleteCascadeResultSet.java:120)
at org.apache.derby.impl.sql.GenericPreparedStatement.executeStmt(GenericPreparedStatement.java:416)
at org.apache.derby.impl.sql.GenericPreparedStatement.execute(GenericPreparedStatement.java:297)
at org.apache.derby.impl.jdbc.EmbedStatement.executeStatement(EmbedStatement.java:1235)
... 24 more

Comments

[Rick Hillegas]

Attaching derby-3964-01-aa-onDeleteSetNull.diff. This patch fixes the NPE triggered when a primary key deletion cascades changes to a foreign key table. Tests are running.

Here's what was going on:

o The cascaded change translated into an UPDATE on the foreign key table.

o During the cascaded change, generation clauses were being evaluated on the pre-images of columns as well as on the after images in the UPDATE row.

o The pre-image referred to a ResultSet whose row was not available at execution time.

o That triggered the NPE.

The fix was to eliminate the useless evaluation of the generation clause on the pre-image of the column.


Touches the following files:

M java/engine/org/apache/derby/impl/sql/compile/DMLModStatementNode.java

The code-generation of generation clauses is changed to only build code for after images. This involves adding an argument to generateGenerationClauses(), flagging whether the statement is an UPDATE.


M java/engine/org/apache/derby/impl/sql/compile/UpdateNode.java
M java/engine/org/apache/derby/impl/sql/compile/InsertNode.java

Adds the extra argument to the callers of generateGenerationClauses.


M java/testing/org/apache/derbyTesting/functionTests/tests/lang/GeneratedColumnsTest.java

Adds a test case.

[Rick Hillegas]

Tests passed cleanly for me on derby-3964-01-aa-onDeleteSetNull.diff except for the heisenbug in the stress multi tests. Committed at subversion revision 722623.

[Chip Hartney]

I cannot tell from this report which versions it occurs in nor which it is fixed in.

I also need to know whether it could be the same as the error I am incurring in both v10.3.3.0 and v10.4.2.0 (but not v10.3.2.1).

It is an error in which I incur a NullPointerException trying to delete a row from a table with ON DELETE referential actions (though not a SET NULL action). The error is exemplified by the following sequence in IJ:

ij> delete from app."LineItem" where "Id" = 60275;
ERROR XJ001: Java exception: ': java.lang.NullPointerException'.
ij> select * from app."LineItem" where "Id" = 60275;
ERROR 08003: No current connection.

The LineItem table has the following constraints:
  ALTER TABLE "APP"."LineItem" ADD CONSTRAINT "LineItem_FK_OrderId" FOREIGN KEY ("OrderId") REFERENCES "APP"."Order" ("Id") ON DELETE CASCADE ON UPDATE NO ACTION;
  ALTER TABLE "APP"."LineItem" ADD CONSTRAINT "LineItem_FK_ProductId" FOREIGN KEY ("ProductId") REFERENCES "APP"."Product" ("Id") ON DELETE RESTRICT ON UPDATE NO ACTION;

[Knut Anders Hatlen]

(Setting affects-version and fix-version to 10.5.0.0.)

Chip,

As I understand this bug, it only affects a new feature in 10.5 (generated columns), so I think you must be seeing something else. Just a guess, but it looks similar to DERBY-2353 (at least if you happen to run with derby.language.logQueryPlan=true). There should be a stack trace for the NullPointerException in derby.log which could give a clue.