SQL Server – How to Query a Remote Server Using a Local Function

functionslinked-serversql server

I am querying a remote server for which I only have read permissions. I set up a local server with a UDF (since I cannot create one on the remote) that I would like to utilize for the query. When I try executing the query, I receive the error

Msg 344, Level 16, State 1
Remote function reference 'localhost\SQLDEV.db.dbo.udf_StripHTML' is not allowed, and the column name 'localhost\SQLDEV' could not be found or is ambiguous.

I tried looking for solutions, but nothing seemed remotely (haha) close to my situation as all other solutions were for executing a remote function against a local query, or trying to pass variables with OPENQUERY, etc. Is there a simple way to achieve this query with only read access to the remote, master db?

SELECT [localhost\SQLDEV].[db].[dbo].[udf_StripHTML](notes.note_text)
FROM event_log AS el
INNER JOIN dbo.progress_note as notes 
on notes.event_log_id = el.event_log_id

Best Answer

Seems (based on the name, anyway) like a pretty basic scalar UDF that just massages strings, won't be subject to a lot of changes over time, and doesn't rely on any data. So, I suggest you make a copy of the function on the source server, and fight whatever rule is preventing you from doing so (it shouldn't be hard if you can justify the use of the function, and describe what kind of hack you're trying to use as a workaround to the rule). Note that the function doesn't have to live in the same database, it just needs to be on the same server.

(Even if the function does rely on data, and it's clear in your case it doesn't, the local copy of the function could reference the data in the other server, using 4-part name(s), without referencing any functions.)

DRY is not always worth pursuing.

Related Solutions

Sql-server – SQL Server update query on linked server causing remote scan

A friend just had a similar problem and rewriting the query solved it.

I know this is an old question, and likely you have worked it out, but for anyone else you could try this and report back...

UPDATE kg
SET 
   IdGarment = IdGarment
   FROM Products p 
   INNER JOIN ZAMStaffRentals r ON r.ProductID = p.UniqueID 
   INNER JOIN ZAMCustomer_Staff s ON r.StaffID = s.UniqueID 
   INNER JOIN ZAMRentalGarments g ON g.StaffRentalID = r.UniqueID 
   INNER JOIN [REMOTE_SERVER].[REMOTE_DB].dbo.t_ProcessIT_Garment kg on g.BarcodeRFID = kg.IdGarment 
   INNER JOIN ZAMKannChanges log on log.GarmentID = g.UniqueID 
   WHERE log.ActionType = 'I' ;

I don't know why this helped, but using the UPDATE "alias" form of the statement meant that the whole UPDATE query was remoted, rather than pulling the data back to the local instance to perform the JOINs.

If anyone has any ideas why this behaviour was seen, I would love to know.

Sql-server – How to query data from a linked server, and pass it parameters to filter by

The performance problem actually had to do with the LEFT OUTER JOIN tables. If I changed them to INNER JOIN, or if I excluded their data from the SELECT columns, the query ran fine.

What I ended up doing was creating a View on the linked server containing all the data I wanted from it, then simply joining to it from the primary server with the #tmpIds table.

I didn't think this would work since I thought joining everything and pulling it down to the second server before filtering was the same as what I was doing now, and would lead to the same performance problem, but surprisingly that doesn't appear to be the case.

CREATE VIEW MyView 
AS

SELECT T1.Id, T2.ColA, ...
FROM Table1 as T1
INNER JOIN Table2 as T2 ON T1.Id = T2.Id
INNER JOIN Table3 as T3 ON T2.Id = T3.Id
LEFT OUTER JOIN Table4 as T4 ON T3.Id = T4.Id
LEFT OUTER JOIN Table5 as T5 ON T4.Id = T5.Id
LEFT OUTER JOIN Table6 as T6 ON T5.Id = T6.Id

GO

and

INSERT INTO #tmpTable (Id, ...)

SELECT T1.Id, T1.ColA, ...
FROM Server.Database.dbo.MyView as T1
INNER JOIN #tmpIds as T ON T1.Id = T.Id

All the joined columns were correctly indexed, however according to this answer

Even though there may be indexing on tables on the remote server, SQL may not be able to take advantage of them while it can build a local query plan that does take advantages of indexing.

And this one

Let the linked server do as much as possible.
It is impossible for SQL Server to optimise a query on a linked server, even another SQL Server

so I am guessing that the query plan used for the query was not using the Indices defined, and SQL Server was generating a poor query plan for the LEFT OUTER JOIN tables.

Best Answer

Related Solutions

Sql-server – SQL Server update query on linked server causing remote scan

Sql-server – How to query data from a linked server, and pass it parameters to filter by

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