Performance of In Operator with OR conditional SQL - sql

Question

I have common clause in Most of the Procedures like
Select * from TABLE A + Joins where <Conditions>
And
(
-- All Broker
('True' = (Select AllBrokers from SiteUser where ID = #SiteUserID))
OR
(
A.BrokerID in
(
Select BrokerID from SiteUserBroker where SiteUserID
= #SiteUserID)
)
)
So basically if the user has access to all brokers the whole filter should not be applied else if should get the list of Broker
I am bit worries about the performance as this is used in lot of procedures and data has started reaching over 100,000 records and will grow soon, so can this be better written?
ANY Ideas are highly appreciated

Answer 1

One of the techniques is to use built dynamic T-SQL statement and then execute it. Since, this is done in stored procedure you are OK and the idea is simple.
DECLARE #DynamicTSQLStatement NVARCHAR(MAX);
SET #DynamicTSQLStatement = 'base query';
IF 'Getting All Brokers is not allowed '
BEGIN;
SET #DynamicTSQLStatement = #DynamicTSQLStatement + 'aditional where clause'
END;
EXEC sp_executesql #DynamicTSQLStatement;
Or instead of using dynamic T-SQL statement you can have two separate queries - one for users seeing all the data and one for users seeing part of the data. This can lead to code duplication.
Another way, is to turn this OR statement in INNER JOIN. You should test the performance in order to be sure you are getting something from it. The idea is to create a temporary table (it can have primary key or indexes if needed) and store all visible broker ids there - if the users sees all, then Select BrokerID from SiteUserBroker and if the users sees a few - Select BrokerID from SiteUserBroker where SiteUserID = #SiteUserID. In the second way, you are going to simplify the whole statement, but be sure to test if performance is improved.
CREATE TABLE #SiteUserBroker
(
[BrokerID] INT PRIMARY KEY
);
INSERT INTO #SiteUserBroker ([BrokerID])
SELECT BrokerID
FROM SiteUserBroker
where SiteUserID = #SiteUserID
OR ('True' = (Select AllBrokers from SiteUser where ID = #SiteUserID));
Select *
from TABLE A
INNER JOIN #SiteUserBroker B
ON A.BrokerID = B.[BrokerID]
-- other joins
where <Conditions>
As we are using INNER JOIN you can add it at the begging. If there are LEFT JOINs after it, it will affect the performance in positive way.

Answer 2

Adding to #gotqn answer, you can add EXISTS instead of IN (Note - This is not complete answer) -
AND EXISTS (
Select 1/0 from SiteUserBroker X
where A.BrokerID = X.BrokerID AND
X.SiteUserID = #SiteUserID
)
I found that Exists performs better than In in some cases. Please verify your case.