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https://issues.apache.org/jira/browse/DERBY-979?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rick Hillegas updated DERBY-979:
--------------------------------
Attachment: testCase.diff
Attaching testCase.diff. This patch rewarms the test case supplied in the
comment above. With this patch, ConcurrencyTest still raises an NPE, although
the NPE has moved. The new NPE is:
Caused by: java.lang.NullPointerException
at
org.apache.derby.impl.store.access.conglomerate.GenericScanController.reopenAfterEndTransaction(GenericScanController.java:1041)
at
org.apache.derby.impl.store.access.conglomerate.GenericScanController.fetchRows(GenericScanController.java:604)
at
org.apache.derby.impl.store.access.heap.HeapScan.fetchNext(HeapScan.java:238)
at
org.apache.derby.impl.sql.execute.TableScanResultSet.getNextRowCore(TableScanResultSet.java:577)
at
org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl.getNextRow(BasicNoPutResultSetImpl.java:477)
at
org.apache.derby.impl.jdbc.EmbedResultSet.movePosition(EmbedResultSet.java:429)
> NullPointerException in store when using holdable resultset to get next tuple
> on a deleted table
> ------------------------------------------------------------------------------------------------
>
> Key: DERBY-979
> URL: https://issues.apache.org/jira/browse/DERBY-979
> Project: Derby
> Issue Type: Bug
> Components: Store
> Environment: All
> Reporter: Andreas Korneliussen
> Priority: Minor
> Attachments: testCase.diff
>
>
> Derby uses table intent locks to prevent a table from being dropped while
> there is an open cursor on it.
> However, for holdable cursors, the lock is released after the commit. This
> allows a drop table command to drop the table. The next call to
> ResultSet.next then get a NullPointerException from the store module.
> A potential fix, could be to handle this situation in store, and to give a
> meaningful error message.
> Transaction history:
> T1: select * from table1
> T1: cursor.next()
> T1: commit
> T2: drop table table1
> T2: commit
> T3: cursor.next()..
> Result: T3 get NullPointerException.
> To reproduce: Add the following testcase to ConcurrencyTest.java (see
> DERBY-934) (hopefully someone commits those tests soon)
> /**
> * Test that as long as an cursor is open on a table, no
> * other transaction can delete the table.
> */
> public void testTableIntentLockWithHoldableCursor()
> throws SQLException
> {
> con.setTransactionIsolation(Connection.TRANSACTION_READ_UNCOMMITTED);
> con.setAutoCommit(true);
> Statement s = con.createStatement(ResultSet.TYPE_FORWARD_ONLY,
> ResultSet.CONCUR_UPDATABLE);
> ResultSet rs = s.executeQuery("select * from t1");
> rs.next();
> updateTuple(rs);
> con.commit();
>
> Connection con2 = getNewConnection();
> con2.setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED);
>
> try {
> PreparedStatement ps2 = con2.prepareStatement
> ("drop table t1");
> ps2.executeUpdate();
> con2.commit();
>
> // .. WHAT happens ?
> rs.next();
> updateTuple(rs);
> } catch (SQLException e) {
> System.out.println(e.getMessage() + ":" + e.getSQLState());
> printStackTrace(e);
> assertEquals("Unexpected SQL state", LOCK_TIMEOUT_SQL_STATE,
> e.getSQLState());
> } finally {
> con2.close();
> }
> }
> java.lang.NullPointerException
> at
> org.apache.derby.impl.store.access.conglomerate.OpenConglomerate.latchPageAndRepositionScan(OpenConglomerate.java:264)
> at
> org.apache.derby.impl.store.access.conglomerate.GenericScanController.fetchRows(GenericScanController.java:613)
> at
> org.apache.derby.impl.store.access.heap.HeapScan.fetchNext(HeapScan.java:207)
> at
> org.apache.derby.impl.sql.execute.TableScanResultSet.getNextRowCore(TableScanResultSet.java:681)
> at
> org.apache.derby.impl.sql.execute.BasicNoPutResultSetImpl.getNextRow(BasicNoPutResultSetImpl.java:474)
> at
> org.apache.derby.impl.jdbc.EmbedResultSet.movePosition(EmbedResultSet.java:371)
> at
> org.apache.derby.impl.jdbc.EmbedResultSet.next(EmbedResultSet.java:320)
> at
> org.apache.derbyTesting.functionTests.tests.jdbcapi.ConcurrencyTest.testTableIntentLockWithHoldableCursor(ConcurrencyTest.java:877)
> ..
> The NullPointerException is wrapped in a SQLException, which just makes the
> bug more confusing for the user.
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