Unicode Parameters

Question

I have a group of reports that query against a non-unicode table (all VARCHAR)
In these reports is a multi-value string parameter that is used to filter data in this table.
In the dataset, I am using this SQL:
Select  Field1
From Data
Where Field2 in (@Parameter)
When SSRS sends this query to the SQL Server, it converts the @Parameter values to Unicode (Prefaces each string with an N)
For example:
Where Field2 in (N'abc',N'def')
The issue with this is that the SQL Server reverts to an index scan, rather than an index seek, causing bad performance, 7-8 seconds instead of <1 second if I run the same query without the unicode strings.
Is there any way to work around this?
Thanks!http://bobp1339.blogspot.com

Answer 1

Work around to overcome SSRS report performance due to UNICODE conversion issue
I have used a new parameter (of type Internal) which collects/duplicates the parameter values as comma separated in string from orig parameter.
In the report Dataset query parse the comma separated string into list using XML trick and load into a variable table.
Use the variable table in WHERE IN clause
Steps:
Create a new Internal parameter (call it InternalParameter1)
Under Default Values -> Specify values : Add Exp : =join( Parameters!OrigParameter1.Value,",")
Pass/Use the InternalParameter1 in your dataset query.
Example code
DECLARE @InternalParameter1 NVARCHAR(MAX)
SET @InternalParameter1 = '100167600,
100167601,
4302853605,
4030753556,
4026938411
--- Load comma separated string to a temp variable table ---
SET ARITHABORT ON
DECLARE @T1 AS TABLE (PARALIST VARCHAR(100))
INSERT @T1 SELECT Split.a.value('.', 'VARCHAR(100)') AS CVS FROM
( SELECT CAST ('<M>' + REPLACE(@InternalParameter1, ',', '</M><M>') + '</M>' AS XML) AS CVS ) AS A CROSS APPLY CVS.nodes ('/M') AS Split(a)
--- Report Dataset query ---
SELECT CONTRACT_NO, report fields… FROM mytable
WHERE CONTRACT_NO IN (SELECT PARALIST FROM @T1) -- Use temp variable table in where clause
Mahesh