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From "Andreas Korneliussen (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-707) providing RowLocation for deleted+purged row to GenericConglomerateController causes nullpointerexception
Date Tue, 15 Nov 2005 16:59:28 GMT
    [ http://issues.apache.org/jira/browse/DERBY-707?page=comments#action_12357711 ] 

Andreas Korneliussen commented on DERBY-707:

The attached files addresses this issue by checking the return value from open_conglom.latchPage(..)
in GenericConglomerateController. Previously the return value has only been used in one of
the four calls to open_conglom.latchPage(..) in this file, the patch also does the same for
all three other places this is called (fetch, delete and replace).
Please review if this could be an appropriate patch for the problem reported. 

> providing RowLocation for deleted+purged row to GenericConglomerateController causes
> ---------------------------------------------------------------------------------------------------------
>          Key: DERBY-707
>          URL: http://issues.apache.org/jira/browse/DERBY-707
>      Project: Derby
>         Type: Bug
>   Components: Store
>  Environment: Java 1.4
>     Reporter: Andreas Korneliussen
>     Assignee: Andreas Korneliussen
>     Priority: Minor
>  Attachments: DERBY-707.diff, DERBY-707.stat
> To provide scrollable updatable resultsets, we will store the RowLocation for every row
in the ResultSet in a temporary table (backingstore hashtable).  The RowLocation is used to
reposition the cursor before an update.
> The problem is when the row for the RowLocation has been deleted and purged by another
transaction.  The update will then fail with a NullPointerException in GenericConglomerateController.replace(..):
> java.lang.NullPointerException
>         at org.apache.derby.impl.store.access.conglomerate.GenericConglomerateController.replace(GenericConglomerateController.java:465)
>         at org.apache.derby.impl.sql.execute.RowChangerImpl.updateRow(RowChangerImpl.java:516)
>         at org.apache.derby.impl.sql.execute.UpdateResultSet.collectAffectedRows(UpdateResultSet.java:577)
>         at org.apache.derby.impl.sql.execute.UpdateResultSet.open(UpdateResultSet.java:276)
>         at org.apache.derby.impl.sql.GenericPreparedStatement.execute(GenericPreparedStatement.java:368)
>         at org.apache.derby.impl.jdbc.EmbedResultSet.updateRow(EmbedResultSet.java:3256)

> It fails when checking if the row has been deleted (not purged) , because pos.current_page
is null:
>         if (pos.current_page.isDeletedAtSlot(pos.current_slot))
>         {
>             ret_val = false;
>         }
> The proposed fix is to use the return value from open_conglom.latchPage(..).  If it returns
false, the RowLocation is invalid (deleted+purged). 

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