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Why DB Pessimistic lock doesn't work

Posted on 2004-10-28
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Last Modified: 2010-04-01
I have code that changes a field in pessimistic lock.
I'm loading two instances of visual C++ with the same code.
in theory when I'm trying to change a field in the same record, I'm supposed
to get an exception, for some reason it doesn't work.
does anyone knows does this happen ?

The code is like this:

m_pDBConn->ConnectionString = _bstr_t( L"DRIVER={Microsoft Access Driver (*.mdb)};"
            L"DBQ=MyDB.mdb;DefaultDir=m:/DB/;");       
_bstr_t bsEmpty = L"";
m_pDBConn->Open( bsEmpty, bsEmpty, bsEmpty, -1 );
hr = m_pRS.CreateInstance(__uuidof(Recordset));
m_pRS->PutRefActiveConnection( m_pDBConn );
m_pTempRS->Open("SELECT * FROM MyTable WHERE ID = 1", vtMissing, adOpenKeyset, adLockPessimistic, adCmdText);
try
{
  m_pRS->Fields->Item["OneField"]->Value =  123;
}
catch (_com_error&)
{
  cout << "why am I'm not here ??? "<< endl;
}
0
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Question by:MagicianH
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7 Comments
 
LVL 39

Expert Comment

by:itsmeandnobodyelse
ID: 12435738
I would assume the exception is thrown when calling recordset Update.

Maybe for a dynamic Recordset it is different.

Regards, Alex

0
 

Author Comment

by:MagicianH
ID: 12456044
If you have a code sample that is working, maybe I coulds copy & try it out...
0
 

Author Comment

by:MagicianH
ID: 12664735
I'm interested in the answer, but nobody answers me...
0
 
LVL 39

Accepted Solution

by:
itsmeandnobodyelse earned 500 total points
ID: 12668644
You asked for a code sample. Unfortunately, i didn't use ADO myself, so i couldn't provide a sample.

However, i'am a pretty experienced database programmer. So, i wouldn't expect 'Pessimistic Locking' is throwing an exception when editing members of the recordset

   m_pRS->Fields->Item["OneField"]->Value =  123; // It's a simple integer assignment

- as that is C++ and the database or recordset isn't involved .

I would expect an exception when you are trying to store while another client had updated in the meantime.

Maybe you should check that suggestion using your own code.

Regards, Alex
0

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