[Also on SuperUser - http://superuser.com/questions/116600/can-i-spead-out-a-long-running-stored-proc-accross-multiple-cpus]
I have a stored procedure in SQL server the gets, and decrypts a block of data. ( Credit cards in this case. )
Most of the time, the performance is tolerable, but there are a couple customers where the process is painfully slow, taking literally 1 minute to complete. ( Well, 59377ms to return from SQL Server to be exact, but it can vary by a few hundred ms based on load )
When I watch the process, I see that SQL is only using a single proc to perform the whole process, and typically only proc 0.
Is there a way I can change my stored proc so that SQL can multi-thread the process? Is it even feasible to cheat and to break the calls in half, ( top 50%, bottom 50% ), and spread the load, as a gross hack? ( just spit-balling here )
My stored proc:
USE [Commerce]
GO
/****** Object: StoredProcedure [dbo].[GetAllCreditCardsByCustomerId] Script Date: 03/05/2010 11:50:14 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[GetAllCreditCardsByCustomerId]
@companyId UNIQUEIDENTIFIER, @DecryptionKey NVARCHAR (MAX)
AS
SET NoCount ON
DECLARE @cardId uniqueidentifier
DECLARE @tmpdecryptedCardData VarChar(MAX);
DECLARE @decryptedCardData VarChar(MAX);
DECLARE @tmpTable as Table
(
CardId uniqueidentifier,
DecryptedCard NVarChar(Max)
)
DECLARE creditCards CURSOR FAST_FORWARD READ_ONLY
FOR Select cardId from CreditCards where companyId = @companyId and Active=1 order by addedBy desc
--2
OPEN creditCards
--3
FETCH creditCards INTO @cardId -- prime the cursor
WHILE @@Fetch_Status = 0
BEGIN
--OPEN creditCards
DECLARE creditCardData CURSOR FAST_FORWARD READ_ONLY
FOR select convert(nvarchar(max), DecryptByCert(Cert_Id('Oh-Nay-Nay'), EncryptedCard, @DecryptionKey)) FROM CreditCardData where cardid = @cardId order by valueOrder
OPEN creditCardData
FETCH creditCardData INTO @tmpdecryptedCardData -- prime the cursor
WHILE @@Fetch_Status = 0
BEGIN
print 'CreditCardData'
print @tmpdecryptedCardData
set @decryptedCardData = ISNULL(@decryptedCardData, '') + @tmpdecryptedCardData
print '@decryptedCardData'
print @decryptedCardData;
FETCH NEXT FROM creditCardData INTO @tmpdecryptedCardData -- fetch next
END
CLOSE creditCardData
DEALLOCATE creditCardData
insert into @tmpTable (CardId, DecryptedCard) values ( @cardId, @decryptedCardData )
set @decryptedCardData = ''
FETCH NEXT FROM creditCards INTO @cardId -- fetch next
END
select CardId, DecryptedCard FROM @tmpTable
CLOSE creditCards
DEALLOCATE creditCards
