[ http://issues.apache.org/jira/browse/DERBY-125?page=all ]
Bryan Pendleton updated DERBY-125:
----------------------------------
Attachment: changes.html
svn.diff
Attached is a proposed change to address bugs 125, 170, 491, and 492, together
with a detailed document discussing the thinking behind the changes and
explaining how they work. Please review this at your convenience and let me
know what you think.
The current patch does not contain any new tests, and I believe that is
mandatory prior to submitting these fixes, so the current patch is not ready to
be submitted. I will be working on adding new tests, but since review of these
changes will require some thought, I thought it would be valuable to put the
change proposal and the accompanying description out there now, while I
continue to work on more testing in the meantime.
thanks,
bryan
> Network Server can send DSS greater than 32K to client, which breaks DRDA
> protocol.
> -----------------------------------------------------------------------------------
>
> Key: DERBY-125
> URL: http://issues.apache.org/jira/browse/DERBY-125
> Project: Derby
> Type: Bug
> Components: Network Server
> Reporter: A B
> Assignee: Bryan Pendleton
> Attachments: changes.html, repro.java, svn.diff
>
> BACKGROUND:
> DRDA protocol, which is the protocol used by Derby Network Server, dictates
> that all DSS objects "with data greater than 32,763 bytes" should be broken
> down into multiple "continuation" DSSes.
> PROBLEM:
> When Network Server receives a "prepareStatement" call that has a very large
> number of parameters, it can end up sending a reply DSS that is greater than
> 32K long to the client; doing so breaks DRDA protocol.
> REPRODUCTION:
> Note that this reproduction does NOT cause a protocol exception against the
> JCC driver--without further investigation, it would appear JCC doesn't mind
> that the DSS is too long. However, other DRDA clients (such as the DB2 ODBC
> client) will see that the data is too long and will fail because of it.
> To reproduce, one can create a simple table and then prepare a statement such
> as:
> SELECT id FROM t1 WHERE id in ( ?, ?, [ ... lots and lots of param markers
> ... ], ?)
> Note that JCC uses deferred prepare by default; when connecting, one must
> append the "deferPrepares=false" attribute to the end of the URL in order to
> reproduce the problem (that or just try to execute the statement, since
> preparation will be done at execution time). When doing the prepare, I added
> a line in the "flush" method of org.apache.derby.impl.drda.DDMWriter.java to
> see how large the reply DSS was, and for cases where the number of parameter
> markers was high, the number of bytes in the single DSS would surpass 32K,
> and thus break protocol.
> NOTES:
> Network Server correctly uses continuation DSSes for LOBs and for result set
> data (data returned as the result of a query) that is greater than 32K. The
> problem appears to be in "other" cases, such as for the prepareStatement call
> described above.
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