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Q198520: BUG: ATL OLE DB Provider Fails When Called from SQL 7.0 Query

Article: Q198520
Product(s): Microsoft C Compiler
Version(s): 6.0,7.0
Operating System(s): 
Keyword(s): kbfile kbpatch kbDatabase kbOLEDB kbSQL kbVC600bug kbATL300bug kbConsumer kbDSupport kb
Last Modified: 13-FEB-2002

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The information in this article applies to:

- Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
- Microsoft Visual C++.NET (2002) 
- Microsoft SQL Server version 7.0 
- Microsoft SQL Server 2000 (all editions) 
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SYMPTOMS
========

SQL Server 7.0 and SQL Server 2000 provide a mechanism for performing
distributed queries against an OLE DB provider. This can be done by using the
new OpenQuery or OpenRowset function. For example, the following SQL statement
performs a query against an OLE DB provider called MyProv by using the command
"Select * from table1":

  Select * from OpenRowset('MyProv', '', 'Select * from table1')

If an ATL wizard-generated OLE DB Provider is queried by using the following
command, an error occurs:

  select * from openrowset ('MyProv.MyProv', '','c:\*.*')

The error message is:

  Server: Msg 7399, Level 16, State 1, Line 1 OLE DB Provider 'atlprov'
  reported an error. The provider ran out of memory

CAUSE
=====

There are a couple of fixes that must be made to the Atldb.h header file. The
fundamental problem exists in two areas:

- The ATL IRowsetImpl::GetColumnInfo method fails to return information
  correctly.

- The IRowsetImpl::GetData method doesn't handle provider-owned memory
  correctly.

RESOLUTION
==========

Atldbfix.h, provided below, is a revised copy of the Atldb.h file included with
Visual Studio Service Pack 5. Search the Atldbfix.h header file for "Fix:" to
find where the changes have been made.

Instead of including the Atldb.h header file in your project, you can replace it
with the Atldbfix.h file, which is provided below in this article. Once you do
that, you will encounter the next error message:

  Server: Msg 7347, Level 16, State 1, Line 1 OLE DB Provider 'Atlprov'
  returned an unexpected data length for the fixed-length column '[].FileName'.
  The expected data length is 260, while the returned data length is 12.

This error is caused by a bug in the ATL wizard-generated code, which returns a
fixed-length string when it should be returning a variable length string of type
DBTYPE_STR.

In the ATL wizard-generated sample provider, change the following two lines in
the provider column map from the following

  PROVIDER_COLUMN_ENTRY("FileName", 4, cFileName)
     PROVIDER_COLUMN_ENTRY("AltFileName", 5, cAlternateFileName)

to the following:

  PROVIDER_COLUMN_ENTRY_STR("FileName", 4, cFileName)
     PROVIDER_COLUMN_ENTRY_STR("AltFileName", 5, cAlternateFileName)

STATUS
======

Microsoft has confirmed this to be a problem in the Microsoft products that are
listed at the beginning of this article.

MORE INFORMATION
================

The following file is available for download from the Microsoft Download
Center:

For Visual C++ 6.0, use:

  Atldbfix.exe
  (http://download.microsoft.com/download/vc60pro/Patch/1/WIN98/EN-US/atldbfix.exe)

Release Date: Jan-07-2002

For additional information about how to download Microsoft Support files, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. Once posted, the file is housed on secure
servers that prevent any unauthorized changes to the file.

Steps to Reproduce Behavior
---------------------------

1. Create an ATL project using the ATL COM AppWizard.

2. Create an ATL OLE DB Provider. On the Insert menu, click New ATL Object, and
  then select Data Access for the category and Provider for the object.

3. Build the ATL OLE DB Provider.

4. Register the provider on a machine with SQL Server 7.0 installed.

5. Run a query against the provider by using the command:

  Select * from OpenRowset('YourProviderName', '', 'c:\*.*')

REFERENCES
==========

For additional information, see the Support WebCast at the following location:

  http://support.microsoft.com/servicedesks/webcasts/wc102699/WC102699.asp

Additional query words: atldbfix

======================================================================
Keywords          : kbfile kbpatch kbDatabase kbOLEDB kbSQL kbVC600bug kbATL300bug kbConsumer kbDSupport kbGrpDSOLEDB kbMDACNoSweep kbSQLProg 
Technology        : kbVCsearch kbSQLServSearch kbAudDeveloper kbSQLServ700 kbSQLServ2000Search kbVC600 kbSQLServ2000 kbVC32bitSearch
Version           : :6.0,7.0
Issue type        : kbbug
Solution Type     : kbpending

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