Using ADO to bypass concurrency checks in a TADOQuery

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5 total messages Started by PaulR Mon, 09 Apr 2007 22:57

#141

Author: PaulR
Date: Mon, 09 Apr 2007 22:57

23 lines
1658 bytes

Using BDS2006, TADOQuery, MSSQL 2005 Express, MS SQLOLEDB.1 driver

I'm trying to see if I can make a TADOQuery to not get a concurrency 
error when I:

1) Select single row in App A
2) App B updates same row
3) App A then updates same row via TADOQuery::Edit() and ::Post() 
methods, but gets concurrency error (specifically "Row cannot be located 
for updating. Some values may have been changed since it was last read")

Ignoring the general issue of should I be doing this or not, does anyone 
know of a way to make App A still be able to overwrite the changes 
posted by App B without making App A reestablish position (i.e., issue 
another select statement)?

I've been playing around with the connection's IsolationLevel, the 
query's CursorType and LockType, but no luck.

Any suggestions?

Thanks,
Paul Rodden

Re: Using ADO to bypass concurrency checks in a TADOQuery

#142

Author: Vassiliev V. V.
Date: Tue, 10 Apr 2007 14:24

39 lines
2466 bytes

Try to set Recordset.Properties['Update Criteria'].Value to adCriteriaKey 
( = 0). After that it should locate row by key, not by all columns - be sure 
that you have PK.

//------------------------------------------
Regards,
Vassiliev V. V.
http://www.managed-vcl.com - using .Net objects in Delphi for Win32 +
ADO.Net
http://www.oledbdirect.com - The fastest way to access MS SQL Server,
MS Jet (Access) and Interbase (through OLEDB)


"PaulR" <nospam_prodden@jwscorp.com_nospam> ???????/???????? ? ???????? 
?????????: news:461ac4e3$1@newsgroups.borland.com...
> Using BDS2006, TADOQuery, MSSQL 2005 Express, MS SQLOLEDB.1 driver
>
> I'm trying to see if I can make a TADOQuery to not get a concurrency error 
> when I:
>
> 1) Select single row in App A
> 2) App B updates same row
> 3) App A then updates same row via TADOQuery::Edit() and ::Post() methods, 
> but gets concurrency error (specifically "Row cannot be located for 
> updating. Some values may have been changed since it was last read")
>
> Ignoring the general issue of should I be doing this or not, does anyone 
> know of a way to make App A still be able to overwrite the changes posted 
> by App B without making App A reestablish position (i.e., issue another 
> select statement)?
>
> I've been playing around with the connection's IsolationLevel, the query's 
> CursorType and LockType, but no luck.
>
> Any suggestions?
>
> Thanks,
> Paul Rodden
>

Re: Using ADO to bypass concurrency checks in a TADOQuery

#143

Author: PaulR
Date: Tue, 10 Apr 2007 17:18

14 lines
1536 bytes

Vassiliev V. V. wrote:
> Try to set Recordset.Properties['Update Criteria'].Value to adCriteriaKey 
> ( = 0). After that it should locate row by key, not by all columns - be sure 
> that you have PK.

Hi, thanks for your suggestion.  I'm working in C++, and I'm having a 
hard time figuring out how to implement this in C++.  The IDE shows the 
[] being overridden, but I can't figure out how to pass in the property 
name.  Doing Properties["Update Criteria"] doesn't work.

Any suggestions?

Thanks,
Paul Rodden

Re: Using ADO to bypass concurrency checks in a TADOQuery

#144

Author: Vassiliev V. V.
Date: Tue, 10 Apr 2007 20:01

56 lines
2717 bytes

It was Delphi code. In C++ it is:


#include <comobj.hpp>

enum ADCPROP_UPDATECRITERIA_ENUM
 { adCriteriaKey = 0,
 adCriteriaAllCols = 1,
 adCriteriaUpdCols = 2,
 adCriteriaTimeStamp = 3
 } ADCPROP_UPDATECRITERIA_ENUM;

If you use C++ Builder 6 you may need to fix its bug with:

namespace System
{
 void __fastcall CheckSafecallResult(HRESULT hr)
 {
  OleCheck(hr);
 }
}

Then:

 ADOQuery1->Active = true;
 ADOQuery1->Recordset->Properties->Item[WideString("Update 
Criteria")]->Value = adCriteriaKey;


//------------------------------------------
Regards,
Vassiliev V. V.
http://www.managed-vcl.com - using .Net objects in Delphi for Win32 +
ADO.Net
http://www.oledbdirect.com - The fastest way to access MS SQL Server,
MS Jet (Access) and Interbase (through OLEDB)




"PaulR" <nospam_prodden@jwscorp.com_nospam> ???????/???????? ? ???????? 
?????????: news:461bc6f0$1@newsgroups.borland.com...
> Vassiliev V. V. wrote:
>> Try to set Recordset.Properties['Update Criteria'].Value to adCriteriaKey 
>> ( = 0). After that it should locate row by key, not by all columns - be 
>> sure that you have PK.
>
> Hi, thanks for your suggestion.  I'm working in C++, and I'm having a hard 
> time figuring out how to implement this in C++.  The IDE shows the [] 
> being overridden, but I can't figure out how to pass in the property name. 
> Doing Properties["Update Criteria"] doesn't work.
>
> Any suggestions?
>
> Thanks,
> Paul Rodden

Re: Using ADO to bypass concurrency checks in a TADOQuery

#145

Author: PaulR
Date: Tue, 10 Apr 2007 22:28

8 lines
1329 bytes

Vassiliev V. V. wrote:
> It was Delphi code. In C++ it is:

That did it, and setting the "Update Criteria" property did what I wanted.

Thank you very much!

Paul Rodden

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