SQL Server 2008 Express Edition file size limitation problem

The SQL Server error I encounter as below:

Could not allocate space for object 'dbo.xxx'.'PK_xxx' in data开发者_如何学编程base 'mainDB' because the 'PRIMARY' filegroup is full. Create disk space by deleting unneeded files, dropping objects in the filegroup, adding additional files to the filegroup, or setting autogrowth on for existing files in the filegroup.

My question is why the MDF file size is limited to only 4GB while the SQL instance running is SQL Server 2008 Express Edition (which I found it supposed to be 10GB instead).

SQL Server 2008 Express supports 4GB.

SQL Server 2008 R2 Express supports 10GB.

Don't forget that the size limit doesn't include the log files (link for SQL Express 2005, but I couldn't find similar for SQL Express 2008 R2 and I don't think this fact has changed). It also doesn't include FILESTREAM data either, which is nice. There are a few useful comments about this here.

This SQL Server Blog entry announced the size increase.