Workaround for calling table-valued function remotely in SQL Server has even more issues

Question

I had a query with a set of parameters that needed to be run multiple times with different parameters, so I wrapped it in a table-valued function.

That table valued function needed called from a remote server. Unfortunately, the call fails on the linked server with the error:

Msg 4122, Level 16, State 1, Line 29
Remote table-valued function calls are not allowed.

Microsoft has acknowledged that "calling a table-valued function remotely" was a feature left out of SQL Server 2008. See: http://connect.microsoft.com/SQLServer/feedback/details/276758/remote-table-valued-function-calls-are-not-allowed

I discovered a workaround using the OPENQUERY syntax, which allows the query to run locally on the remote server and then return the result set. See: http://social.msdn.microsoft.com/Forums/en/transactsql/thread/7a6e4aa1-630b-4ad5-aee5-15139987adbd

Unfortunately, this workaround needed a workaround, because it requires a string as an argument, meaning you can't pass a variable using the OPENQUERY syntax and you can't even concatenate a string in it, like if you want to include variables that you want to pass to the remote table-valued function. The workaround for the workaround is to explicitly build the OPENQUERY query with dynamic SQL, ensuring a normal string gets passed to it. See: http://social.msdn.microsoft.com/Forums/en-US/transactsql/thread/0847ad24-0dfe-4ae1-9788-5516c7830f40/

Still, another problem results from this. Even after ensuring all the quotes and double-quotes and quadruple quotes are embedded correctly so the whole thing can be passed through exec sp_executesql there is still a problem:

When the query ultimately calls the table-valued function, I get the error:

OLE DB provider "SQLNCLI10" for linked server "MY_REMOTE_SERVER_NAME" returned message "Deferred prepare could not be completed.".
Msg 7416, Level 16, State 1, Procedure MyTableValuedFunctionName, Line 22
Access to the remote server is denied because no login-mapping exists.

I'm not sure why I'm getting this error, because the mapping exists for my username, and if I simply replace the table-valued function with an actual table, it returns the results fine. The problem occurs with the OPENQUERY statement, regardless of whether it's executed with sp_executesql or not, and as I said it only occurs when calling a table-valued function.

Any ideas how to solve this?

Answer 1

Have you tried this variation - basically you push the call to the function to happen locally on the remote box:

EXEC REMOTE_SERVER_NAME.db_name..sp_executesql N'SELECT * 
  FROM dbo.MyTableValuedFunctionName();';

Answer 2

In case you can't solve it by calling an EXEC (because you're calling this function from another function or you're trying to do something like INSERT EXEC but you can't nest it, etc.), here is a workarround that solved this problem for me:

You can create a function in your local server that runs the same query as the remote function (asuming you know the implementation of the remote function) since you can access tables and "static-called-functions" (by openquery) with no problems.

In example, if the remote function is something like this:

CREATE FUNCTION dbo.[remote_function] (@param1 varchar(200))
RETURNS TABLE AS RETURN 
( SELECT col1, col2, col3 FROM [remote_db].[dbo].[remote_table] where col1 = @param1)
GO

You can create a function in your local server:

CREATE FUNCTION dbo.[local_function] (@param1 varchar(200))
RETURNS TABLE AS RETURN 
( SELECT col1, col2, col3 FROM [remote_server].[remote_db].[dbo].[remote_table] where col1 = @param1)
GO

And then just query your new function as you want...

SELECT col1, col2, col3 FROM dbo.local_function(@param1);
GO

It should work with no problems.