Forcing a SQL Remote Query to filter remotely instead of locally

Question

I have a MS SQL Query that is pulling data via from a remote server. The data that I'm pulling down needs to be filtered by a date that is determined at run time.. When I run the query like this:

SELECT * FROM SERVER.Database.dbo.RemoteView
WHERE EntryDate > '1/1/2009'

then the filter is applied remotely... However, I don't actually want to use '1/1/2009' as the date - I want the date to be supplied by a user-defined function, like this:

SELECT * FROM SERVER.Database.dbo.RemoteView
WHERE EntryDate > dbo.MyCustomCLRDateFunction()

where the function is a custom CLR scalar-valued function that returns a date time... (You may ask why I need to do this... the details are a bit complicated, so just trust me - I have to do it this way.)

When I run this query, the remote query is NOT filtered remotely - the filtering is done after all of the data is pulled down (400,000 rows vs 100,000 rows) and it makes a significant difference.

Is there a way that I can force the query to do the filtering remotely?

Thanks!

Answer 1

You need to properly decorate your CLR function to mark it as Deterministic, Precise and Data Access/System Data Access as DataAccessKind.None.

Answer 2

Can't you just send a query like this, or does the clr function have to actually be called inside the select statement?

Declare @datetime datetime
Set @datetime = dbo.MyCustomCLRDateFunction()

SELECT * FROM SERVER.Database.dbo.RemoteView
WHERE EntryDate > @datetime

Answer 3

You could also construct a string and use an openquery ...

set @sqlString =
 ' select into myTable from openquery
    (remoteServer,
        "SELECT * FROM Database.dbo.RemoteView WHERE EntryDate > %DTSTART"
    )
 '

set @sqlString  = 
    replace(@sqlString, '%DTSTART', 
                        (select cast(dbo.MyCustomCLRDateFunction() as char(8)) 
           )

EXECUTE sp_executesql @stmt=@sqlString