Thursday, October 08, 2009

Command Parameter Handling

I recently got an email from an interested reader pointing out an error in the SQL command parameter handling OLE DB Client code. If you remember my previous ramblings on this issue, the OLE DB provider for SQL Compact is unable to handle BLOB SQL command parameter through storage objects. This means that you must provide some information about the BLOB before using the command, just like you have to do if you use the ADO .NET stack. Now, if you look at the CCommand::CreateParameter method you will see the error:

ULONG nParamSize = bIsLong ? 1024 : pParamInfo->ulParamSize;

Let me assure you that I was not taking any medication (or smoking funny stuff) when I wrote this line. This is a piece of code that I just did not return to so the error crept in and started to create lots of memory leaks. Solving this issue is not a simple matter of correcting this line to:

ULONG nParamSize = pParamInfo->ulParamSize;

Like I said, we must specify all the BLOB parameter sizes before we prepare the command and this means that CCommand::Prepare must also change. Instead of getting parameter information in the call to Prepare, the user will have the option of calling another method to get this information. In any case, there must be an option to provide custom command parameters. This is the topic of my next post.

No comments: