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From Army <a...@golux.com>
Subject [DEFECT] Network Server Protocol error when select fails and "order by" is specified
Date Thu, 09 Sep 2004 18:04:01 GMT


If, when using the Network Server, one tries to execute a select 
statement that fails because of an SQL exception (ex. divide-by-zero), 
and if an "order by" clause is specified as part of the select, the 
server will throw a distributed protocol exception, instead of the 
appropriate error.

Repro (using the "ij" utility)

ij> connect 'jdbc:derby:net://localhost:1527/myDB:user=u;password=p;';
ij> create table t1 (i int, j int);
0 rows inserted/updated/deleted
ij> insert into t1 values (2,0);
1 row inserted/updated/deleted

-- Without an "order by" it's fine...
-- (22012 ==> "Attempt to divide by zero.", which is fine)

ij> select {fn mod(i,j)} from t1;
ERROR 22012: DB2 SQL error: SQLCODE: -1, SQLSTATE: 22012, SQLERRMC: 22012

-- With an order by, it dies...

ij> select {fn mod(i,j)} from t1 order by 1;

ERROR 58009: Execution failed due to a distribution protocol error that 
caused deallocation of the conversation. A DRDA Data Stream Syntax Error 
was detected. Reason: 0x13


The problem is in the DRDAConnThread.java file, "processCommands(...)" 
method, in the "case CodePoint.OPNQRY" block of code. In the case of an 
SQL exception, there's a call to "writer.clearBuffer()" that is used to 
ensure that _only_ an OPNQFLRM is sent back to the client, not the 
OPNQRYRM and/or QRYDSC that may have been written to buffer before the 
OPNQFLRM. That call to "clearBuffer" has to be replaced with something 
smarter, so that instead of doing a full clear (which causes the problem 
shown above), it only backs out the buffer writes that it has made since 
beginning the "case CodePoint.OPNQRY" block...


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