Problem in opening recordset

Glenn T. Jayaputera -- gtj@nunkeen.apana.org.au
Tuesday, January 07, 1997

Environment: MSVC 1.52/Win 95

Why the following section of the codes produce "Can't open any more tables or queries"
Any help + pointer are greatly appreciated

for ( int nIdx=0; nIdx < 500; nIdx++ )
{
  CDatabase SomeDB;
  SomeDB.Open( .... );   // Assume successfull in opening the database

   CRecordset *pSet = new CRecordset( &SomeDB );
   pSet->Open( ...blah..blah..blah.. );
   :
   // do something..
   :
   pSet->Close();
   delete pSet;
   SomeDB.Close();
}


After a number of iteration I do get "Can't open any more tables or queries" message.  I just 
dont quite understand why I do get that message where in fact I am closing the record set and 
database in each of the iterations..

thanks in advance
glenn tesla

---

Dana M. Epp -- eppdm@uniserve.com
Wednesday, January 08, 1997

[Mini-digest: 2 responses]

I believe it is very inefficient to open and close like this. Not only is
this slow.. but you are causing so much extra load on the database, which I
don't think is needed. I may be taking you on a tangent here, as most of
this comes from experience with 4.x releases for the database stuff,
however, I would assume the underlying principles still work back to 1.52.
Someone in the list may be able to verifiy if this is do-able back at 1.52.

Here is a few issues you may want to think about:

1) You only need one instance of the CDatabase. As such, I would move the
CDatabase outside of your loop. 

2) For efficiency, it may be better by simply making one call to Open.

3) Your methodology on opening the data seems very different. Why not simply
open a CRecordSet (I usually use the ClassWizard and design a derived class
to take care of this, which also will set up the Dynaset and bind fields for
ya.), and work with it from there with requeries(See #4)?

4) You may find simply requerying a better alternative. If you Requery
instead of opening and closing each time.. you may get better results, and
definetly speed up the loop. This may put you on a better direction... or a
far off tangent 

CDatabase SomeDB;      // You only need to create the Database once. 
SomeDB.Open(...); // Assume successfull in opening the database

CRecordset *pSet = new CRecordset( &SomeDB );
try{
   pSet->Open( .... ); // Make your inital opening of the RecordSet.
}
catch( CDBException* e )
{
    AfxMessageBox( e->m_strError, MB_OK|MB_ICONEXCLAMATION );
    e->Delete();
    return;
}

for ( int nIdx=0; nIdx < 500; nIdx++ )
{
   pSet->Requery();        
   :
   // do something..
   :
}

pSet->Close();
delete pSet;

SomeDB.Close();


At 06:02 PM 1/7/97 +1100, you wrote:
>Environment: MSVC 1.52/Win 95
>
>Why the following section of the codes produce "Can't open any more tables
or queries"
>Any help + pointer are greatly appreciated
>
>for ( int nIdx=0; nIdx < 500; nIdx++ )
>{
>  CDatabase SomeDB;
>  SomeDB.Open( .... );   // Assume successfull in opening the database
>
>   CRecordset *pSet = new CRecordset( &SomeDB );
>   pSet->Open( ...blah..blah..blah.. );
>   :
>   // do something..
>   :
>   pSet->Close();
>   delete pSet;
>   SomeDB.Close();
>}
>
>
>After a number of iteration I do get "Can't open any more tables or
queries" message.  I just 
>dont quite understand why I do get that message where in fact I am closing
the record set and 
>database in each of the iterations..
>
>thanks in advance
>glenn tesla
>
>
PC'ing you,                     
Dana M. Epp          
eppdm@uniserve.com
http://bedrock.cyberhq.com/dana

     "How can one work with the technology of today, using yesterdays
      software and methods, and still be on the leading edge tomorrow?
      Why settle for less... I won't! "

-----From: "Michael J. Morel" 

I'm not sure if this is related, but I recall running into a similar 
problem where CDatabase did not completely cleanup when closed.  My 
solution was to allocate it on the heap also.  Does this work any 
differently?
for ( int nIdx=0; nIdx < 500; nIdx++ )
{
  CDatabase* pSomeDB = new CDatabase();
  pSomeDB->Open( .... );   // Assume successfull in opening the database

   CRecordset *pSet = new CRecordset( &SomeDB );
   pSet->Open( ...blah..blah..blah.. );
   :
   // do something..
   :
   pSet->Close();
   delete pSet;
   pSomeDB->Close();
         delete pSomeDB;
}

Mike Morel
mmorel@mushroomsoft.com
Mushroom Software
Home of MFC For Yourself
http://www.mushroomsoft.com


----------
From: 	Glenn T. Jayaputera[SMTP:gtj@nunkeen.apana.org.au]
Sent: 	Tuesday, January 07, 1997 1:02 PM
To: 	mfc-l@netcom.com
Subject: 	Problem in opening recordset

Environment: MSVC 1.52/Win 95

Why the following section of the codes produce "Can't open any more tables 
or queries"
Any help + pointer are greatly appreciated

for ( int nIdx=0; nIdx < 500; nIdx++ )
{
  CDatabase SomeDB;
  SomeDB.Open( .... );   // Assume successfull in opening the database

   CRecordset *pSet = new CRecordset( &SomeDB );
   pSet->Open( ...blah..blah..blah.. );
   :
   // do something..
   :
   pSet->Close();
   delete pSet;
   SomeDB.Close();
}


After a number of iteration I do get "Can't open any more tables or 
queries" message.  I just
dont quite understand why I do get that message where in fact I am closing 
the record set and
database in each of the iterations..

thanks in advance
glenn tesla

---

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