Table Valued Function Killing My Query Performance

Question

I was having a horrible time today trying to get a query to perform the way I would expect. I had to make a slight change to a table valued function that lives in the query

Answer 1

On the SQL Server 2014 we were able to solve our issue by inserting table value function data into temp table and then doing join on it. Instead of doing a join directly to table value function.

This improved our execution time from 2 min to 4 secs.

Here is an example that worked for our team:

--SLOW QUERY (2 min):

DECLARE @id INT = 1;

SELECT * 
FROM [data].[someTable] T
INNER JOIN [data].[tableValueFunction](@id) TVF ON TVF.id = T.id;

--FAST QUERY (4 sec):

DECLARE @id INT = 1;

SELECT * 
INTO #tableValueFunction
FROM [data].[tableValueFunction](@id) TVF

SELECT * 
FROM [data].[someTable] T
INNER JOIN #tableValueFunction TVF ON TVF.id = T.id;