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From "Knut Anders Hatlen (JIRA)" <derby-...@db.apache.org>
Subject [jira] Updated: (DERBY-1468) Server returns data when it receives a QRYROWSET value of zero on an OPNQRY, which doesn't follow DRDA protocol.
Date Fri, 30 Jun 2006 19:36:31 GMT
     [ http://issues.apache.org/jira/browse/DERBY-1468?page=all ]

Knut Anders Hatlen updated DERBY-1468:
--------------------------------------

    Attachment: derby-1468-v1.diff
                derby-1468-v1.stat

The attached patch (v1) disables pre-fetching for LMTBLKPRC when QRYROWSET=0. Army could you
please see if solves the issue with the ODBC driver?

Since there is no way I know of to reproduce the bug with the network client driver, I have
added a test case to the protocol test which sends an OPNQRY for a scrollable cursor with
QRYROWSET=0. The test case fails without the patch and succeeds with the patch. I think the
test case mimics the behaviour of the ODBC driver.

One thing to note about the patch: It does revert the handling of the specific case to pre-822
behaviour, but it does nothing with writeQRYDTA and writeFDODTA to make them handle QRYROWSET=0.
writeQRYDTA() can still be called with QRYROWSET=0 on EXCSQLSTT. I'm not sure whether that
is a problem, and the code that enables this was not touched by DERBY-822. EXCSQLSTT should
probably have a similar fix for completeness. (A possible way to try to provoke this with
the ODBC driver could be to execute a stored procedure that returns a scrollable result set.)

Derbyall runs cleanly with the patch.

> Server returns data when it receives a QRYROWSET value of zero on an OPNQRY, which doesn't
follow DRDA protocol.
> ----------------------------------------------------------------------------------------------------------------
>
>          Key: DERBY-1468
>          URL: http://issues.apache.org/jira/browse/DERBY-1468
>      Project: Derby
>         Type: Bug

>   Components: Network Server
>     Versions: 10.2.0.0
>     Reporter: A B
>     Assignee: Knut Anders Hatlen
>  Attachments: derby-1468-v1.diff, derby-1468-v1.stat
>
> When a client sends a QRYROWSET value of zero to the server, DRDA indicates that the
server should not return any rows.  But the current Derby Server treats a qryrowset value
of 0 (zero) the same as it does a value of 1 (one) and thus performs pre-fetching (as of DERBY-822),
which it shouldn't do.
> As a result, clients that send a QRYROWSET of 0 and do not expect data could see unexpected
results--for example, the DB2 ODBC driver will return the first row of data twice for scrollable
cursors because of this issue.
> Relevant discussion:
> http://article.gmane.org/gmane.comp.apache.db.derby.devel/22659
> Some quotes from DRDA manuals:
> 1) DRDA Manual v3 for OPNQRY:
> The qryrowset parameter specifies whether a rowset of rows is to be returned with the
command.  This is only honored for non-dynamic scrollable cursors (QRYATTSNS not equal to
QRYSNSDYN) and for non-scrollable cursors conforming to the limited block query protocol.
 The target server fetches no more than the requested number of rows. It may fetch fewer rows
if it is restricted by extra query block limits, or if a fetch operation results in a negative
SQLSTATE or an SQLSTATE of 02000.
> 2) Page 698 of V.3 says:
> A QRYROWSET value of zero on the OPNQRY and EXCSQLSTT commands instructs the server to
return no rows with the OPNQRYRM for the cursor or result set. A QRYROWSET value of zero on
the CNTQRY command is invalid for non-rowset cursors and results in the application server
generating a SYNTAXRM with a SYNERRCD value of '15'x (reserved value not allowed).

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