calculated fields w/user defined functions

Hi,
In the new application we are extensively using calculated fields that
consist of user defined functions that query multiple tables in the
database. Does anybody know of any limitations or drowbacks of using
user-defined functions in calculated fields (performance, locking, etc) Here
is an example of the most complex user defined function we have:
CREATE FUNCTION dbo.PayrollDetail_Subtotal
(
@.PayrollDetailID int,
@.CoverageType varchar(25)
)
RETURNS decimal(19,4) AS
BEGIN
DECLARE
@.AmountCap AS decimal(19,2),
@.AmountEffective as decimal (19,2),
@.AssignmentID as int,
@.PolicyID1 as int,
@.PolicyID2 as int,
@.PolicyTo1 as datetime,
@.PolicyFrom2 as datetime,
@.WorkCode AS int,
@.Result AS decimal(19,2),
@.PayrollFrom AS datetime,
@.PayrollTo AS datetime,
@.PayrollType AS varchar(50),
@.PayrollHeaderID AS int,
@.Composite1 AS decimal(19,2),
@.Composite2 AS decimal(19,2),
@.Territory1 AS int,
@.TerritoryMod1 as decimal(10,4),
@.WCRateID1 AS int,
@.WCRate1 AS decimal(19,4),
@.WCFactor1 AS varchar(50)
SET @.Result = 0
/* Payroll Header ID and dates*/
/* NULL for PayrollHeader is not allowed in tblPayrollDetail */
SELECT @.PayrollHeaderID = PayrollHeaderID, @.WorkCode=lkWorkCodeID,
@.AmountCap=AmountCap, @.AmountEffective = AmountEffective from
tblPayrollDetail where PayrollDetailID = @.PayrollDetailID;
/* NULL is not allowed for DateFrom, DateTo in tblPayrollHeader */
SELECT @.PayrollFrom = DateFrom, @.PayrollTo = DateTo, @.PayrollType = PayrollType, @.AssignmentID = AssignmentID from tblPayrollHeader WHERE
PayrollHeaderID = @.PayrollHeaderID
SELECT @.PolicyID1=CE.CoverageEntryID, @.Composite1 = CE.CompositeRating,
@.PolicyTo1 = CE.DateExpiration from tblCoverageAssignment A INNER JOIN
tblCoverageEntry CE ON A.CoverageEntryID = CE.CoverageEntryID AND
A.CoverageType=@.CoverageType WHERE
CE.DateEffective<=@.PayrollFrom AND @.PayrollFrom<=CE.DateExpiration
SELECT @.PolicyID2=CE.CoverageEntryID, @.Composite2 = CE.CompositeRating,
@.PolicyFrom2 = CE.DateEffective from tblCoverageAssignment A INNER JOIN
tblCoverageEntry CE ON A.CoverageEntryID = CE.CoverageEntryID AND
A.CoverageType=@.CoverageType WHERE
CE.DateEffective<=@.PayrollTo AND @.PayrollTo<=CE.DateExpiration
/* Composite Rating in tblCoverageEntry has default of 0 */
if (@.PolicyID1 is null) OR (@.Composite1 = 0) OR (@.PolicyID2 is null) OR
(@.Composite2=0)
return 0
ELSE
BEGIN
IF (@.PolicyID1 = @.PolicyID2)
/* ++++++CASE 1 : Payroll dates fall within the same policy year
+++++++*/
BEGIN
/* work code rate */
SELECT @.WCRateID1 = WorkCodeRateID, @.WCRate1 = RateAmount, @.WCFactor1 = Factor from tblWorkCodeRate where CoverageEntryID = @.PolicyID1 and
lkWorkCodeID = @.WorkCode
IF (@.WCRateID1 is null)
return 0
ELSE
BEGIN
IF @.WCFactor1 = 'Rate/100'
SELECT @.Result = @.WCRate1*0.01
ELSE
BEGIN
IF @.WCFactor1='Rate/1000'
SELECT @.Result = @.WCRate1*0.001
ELSE
SELECT @.Result = @.WCRate1
END
/* base */
IF (@.CoverageType = 'Excess' OR @.CoverageType='GL')
SELECT @.Result = @.Result*@.AmountEffective
IF (@.CoverageType = 'WC')
BEGIN
IF @.AmountCap =0
SELECT @.Result = @.Result * @.AmountEffective
ELSE
SELECT @.Result = @.Result * @.AmountCap
END
/* Territory */
SELECT @.Territory1 = A.lkTerritoryID from tblPayrollHeader PH INNER
JOIN tblAssignment A ON PH.AssignmentID = A.AssignmentID WHERE
PH.PayrollHeaderID = @.PayrollHeaderID
if (@.Territory1 is null)
SELECT @.Result = @.Result * @.Composite1
ELSE
BEGIN
SELECT @.TerritoryMod1= Modifier from tblTerritoryModifier WHERE
lkTerritoryID = @.Territory1 and WorkCodeRateID = @.WCRateID1
IF (@.TerritoryMod1 is NULL) OR (@.TerritoryMod1=0)
SELECT @.Result = @.Result * @.Composite1
ELSE
SELECT @.Result = @.Result * @.Composite1 * @.TerritoryMod1
END
END
END
ELSE
/* IF Payroll falls under 2 policy years */
BEGIN
DECLARE
@.Territory2 AS int,
@.TerritoryMod2 as decimal(10,4),
@.WCRateID2 AS int,
@.WCRate2 AS decimal(19,4),
@.WCFactor2 AS varchar(50),
@.Result1 AS decimal(19,4),
@.Result2 AS decimal(19,4),
@.NoDays1 AS int,
@.NoDays2 AS int,
@.PayrollLength AS int
/* +++POLICY YEAR 1+++ */
/* work code rate */
SELECT @.WCRateID1 = WorkCodeRateID, @.WCRate1 = RateAmount, @.WCFactor1 = Factor from tblWorkCodeRate where CoverageEntryID = @.PolicyID1 and
lkWorkCodeID = @.WorkCode
IF (@.WCRateID1 is null)
SELECT @.Result1 = 0
ELSE
BEGIN
IF @.WCFactor1 = 'Rate/100'
SELECT @.Result1 = @.WCRate1*0.01
ELSE
BEGIN
IF @.WCFactor1='Rate/1000'
SELECT @.Result1 = @.WCRate1*0.001
ELSE
SELECT @.Result1 = @.WCRate1
END
/* base */
SELECT @.NoDays1= DATEDIFF(day,@.PayrollFrom,@.PolicyTo1)
SELECT @.NoDays2= DATEDIFF(day,@.PayrollTo,@.PolicyFrom2)
SELECT @.PayrollLength = @.NoDays1+@.NoDays2
/* no of days for Policy Year 1= DateFrom - DateExpiration for Policy
Year 1 */
IF (@.CoverageType = 'Excess' OR @.CoverageType='GL')
SELECT @.Result1 = @.Result1*((@.AmountEffective/@.PayrollLength)*@.NoDays1)
IF (@.CoverageType = 'WC')
BEGIN
IF @.AmountCap =0
SELECT @.Result1 = @.Result1*((@.AmountEffective/@.PayrollLength)*@.NoDays1)
ELSE
SELECT @.Result1 = @.Result1* ((@.AmountCap/@.PayrollLength)*@.NoDays1)
END
/* Territory */
SELECT @.Territory1 = A.lkTerritoryID from tblPayrollHeader PH INNER
JOIN tblAssignment A ON PH.AssignmentID = A.AssignmentID WHERE
PH.PayrollHeaderID = @.PayrollHeaderID
if (@.Territory1 is null)
SELECT @.Result1 = @.Result1 * @.Composite1
ELSE
BEGIN
SELECT @.TerritoryMod1= Modifier from tblTerritoryModifier WHERE
lkTerritoryID = @.Territory1 and WorkCodeRateID = @.WCRateID1
IF (@.TerritoryMod1 is NULL) OR (@.TerritoryMod1=0)
SELECT @.Result1 = @.Result1 * @.Composite1
ELSE
SELECT @.Result1 = @.Result1 * @.Composite1 * @.TerritoryMod1
END
END
/* +++POLICY YEAR 2+++ */
/* work code rate */
SELECT @.WCRateID2 = WorkCodeRateID, @.WCRate2 = RateAmount, @.WCFactor2 = Factor from tblWorkCodeRate where CoverageEntryID = @.PolicyID2 and
lkWorkCodeID = @.WorkCode
IF (@.WCRateID2 is null)
SELECT @.Result2 = 0
ELSE
BEGIN
IF @.WCFactor2 = 'Rate/100'
SELECT @.Result2 = @.WCRate2*0.01
ELSE
BEGIN
IF @.WCFactor2='Rate/1000'
SELECT @.Result2 = @.WCRate2*0.001
ELSE
SELECT @.Result2 = @.WCRate2
END
/* base */
IF (@.CoverageType = 'Excess' OR @.CoverageType='GL')
SELECT @.Result2 = @.Result2*((@.AmountEffective/@.PayrollLength)*@.NoDays2)
IF (@.CoverageType = 'WC')
BEGIN
IF @.AmountCap =0
SELECT @.Result2 = @.Result2*((@.AmountEffective/@.PayrollLength)*@.NoDays2)
ELSE
SELECT @.Result2 = @.Result2* ((@.AmountCap/@.PayrollLength)*@.NoDays2)
END
/* Territory */
SELECT @.Territory2 = A.lkTerritoryID from tblPayrollHeader PH INNER
JOIN tblAssignment A ON PH.AssignmentID = A.AssignmentID WHERE
PH.PayrollHeaderID = @.PayrollHeaderID
if (@.Territory2 is null)
SELECT @.Result2 = @.Result2 * @.Composite2
ELSE
BEGIN
SELECT @.TerritoryMod2= Modifier from tblTerritoryModifier WHERE
lkTerritoryID = @.Territory2 and WorkCodeRateID = @.WCRateID2
IF (@.TerritoryMod2 is NULL) OR (@.TerritoryMod2=0)
SELECT @.Result2 = @.Result2 * @.Composite2
ELSE
SELECT @.Result2 = @.Result2 * @.Composite2 * @.TerritoryMod2
END
END
SELECT @.Result = @.Result1 + @.Result2
END
END
return @.Result
ENDUser defined functions in computed columns perform pretty badly compared to
plain SQL. The reason is that behind the season the function works as a
cursor, all the work is done on a row-by-row basis. You probably won't
notice that much if you only have a few rows, but once you get to a largish
amount (say 1000+) performance will go out of the window.
I did some testing the other day and SELECT * on a table with around 8000
rows had a subsecond return time without a computed column with a UDF, but
20+ seconds with a computed column with a UDF. On that basis I decided to
redesign the solution so it would work without a computed column, which
involved creating a few new tables, and performance is now acceptable.
So, you can use it, but only if your table has a very small number of rows,
or if you have a larger table and you are sure you will never ever have a
table scan on that table.
"ilona" <ieshulman@.sseinc.com> wrote in message
news:etjJPzjRDHA.1688@.TK2MSFTNGP11.phx.gbl...
> Hi,
> In the new application we are extensively using calculated fields that
> consist of user defined functions that query multiple tables in the
> database. Does anybody know of any limitations or drowbacks of using
> user-defined functions in calculated fields (performance, locking, etc)
Here
> is an example of the most complex user defined function we have:
>
> CREATE FUNCTION dbo.PayrollDetail_Subtotal
> (
> @.PayrollDetailID int,
> @.CoverageType varchar(25)
> )
> RETURNS decimal(19,4) AS
> BEGIN
> DECLARE
> @.AmountCap AS decimal(19,2),
> @.AmountEffective as decimal (19,2),
> @.AssignmentID as int,
> @.PolicyID1 as int,
> @.PolicyID2 as int,
> @.PolicyTo1 as datetime,
> @.PolicyFrom2 as datetime,
> @.WorkCode AS int,
> @.Result AS decimal(19,2),
> @.PayrollFrom AS datetime,
> @.PayrollTo AS datetime,
> @.PayrollType AS varchar(50),
> @.PayrollHeaderID AS int,
> @.Composite1 AS decimal(19,2),
> @.Composite2 AS decimal(19,2),
> @.Territory1 AS int,
> @.TerritoryMod1 as decimal(10,4),
> @.WCRateID1 AS int,
> @.WCRate1 AS decimal(19,4),
> @.WCFactor1 AS varchar(50)
>
> SET @.Result = 0
> /* Payroll Header ID and dates*/
> /* NULL for PayrollHeader is not allowed in tblPayrollDetail */
> SELECT @.PayrollHeaderID = PayrollHeaderID, @.WorkCode=lkWorkCodeID,
> @.AmountCap=AmountCap, @.AmountEffective = AmountEffective from
> tblPayrollDetail where PayrollDetailID = @.PayrollDetailID;
> /* NULL is not allowed for DateFrom, DateTo in tblPayrollHeader */
> SELECT @.PayrollFrom = DateFrom, @.PayrollTo = DateTo, @.PayrollType => PayrollType, @.AssignmentID = AssignmentID from tblPayrollHeader WHERE
> PayrollHeaderID = @.PayrollHeaderID
> SELECT @.PolicyID1=CE.CoverageEntryID, @.Composite1 = CE.CompositeRating,
> @.PolicyTo1 = CE.DateExpiration from tblCoverageAssignment A INNER JOIN
> tblCoverageEntry CE ON A.CoverageEntryID = CE.CoverageEntryID AND
> A.CoverageType=@.CoverageType WHERE
> CE.DateEffective<=@.PayrollFrom AND @.PayrollFrom<=CE.DateExpiration
> SELECT @.PolicyID2=CE.CoverageEntryID, @.Composite2 = CE.CompositeRating,
> @.PolicyFrom2 = CE.DateEffective from tblCoverageAssignment A INNER JOIN
> tblCoverageEntry CE ON A.CoverageEntryID = CE.CoverageEntryID AND
> A.CoverageType=@.CoverageType WHERE
> CE.DateEffective<=@.PayrollTo AND @.PayrollTo<=CE.DateExpiration
> /* Composite Rating in tblCoverageEntry has default of 0 */
> if (@.PolicyID1 is null) OR (@.Composite1 = 0) OR (@.PolicyID2 is null) OR
> (@.Composite2=0)
> return 0
> ELSE
> BEGIN
> IF (@.PolicyID1 = @.PolicyID2)
> /* ++++++CASE 1 : Payroll dates fall within the same policy year
> +++++++*/
> BEGIN
> /* work code rate */
> SELECT @.WCRateID1 = WorkCodeRateID, @.WCRate1 = RateAmount, @.WCFactor1 => Factor from tblWorkCodeRate where CoverageEntryID = @.PolicyID1 and
> lkWorkCodeID = @.WorkCode
> IF (@.WCRateID1 is null)
> return 0
> ELSE
> BEGIN
> IF @.WCFactor1 = 'Rate/100'
> SELECT @.Result = @.WCRate1*0.01
> ELSE
> BEGIN
> IF @.WCFactor1='Rate/1000'
> SELECT @.Result = @.WCRate1*0.001
> ELSE
> SELECT @.Result = @.WCRate1
> END
> /* base */
> IF (@.CoverageType = 'Excess' OR @.CoverageType='GL')
> SELECT @.Result = @.Result*@.AmountEffective
> IF (@.CoverageType = 'WC')
> BEGIN
> IF @.AmountCap =0
> SELECT @.Result = @.Result * @.AmountEffective
> ELSE
> SELECT @.Result = @.Result * @.AmountCap
> END
> /* Territory */
> SELECT @.Territory1 = A.lkTerritoryID from tblPayrollHeader PH INNER
> JOIN tblAssignment A ON PH.AssignmentID = A.AssignmentID WHERE
> PH.PayrollHeaderID = @.PayrollHeaderID
> if (@.Territory1 is null)
> SELECT @.Result = @.Result * @.Composite1
> ELSE
> BEGIN
> SELECT @.TerritoryMod1= Modifier from tblTerritoryModifier WHERE
> lkTerritoryID = @.Territory1 and WorkCodeRateID = @.WCRateID1
> IF (@.TerritoryMod1 is NULL) OR (@.TerritoryMod1=0)
> SELECT @.Result = @.Result * @.Composite1
> ELSE
> SELECT @.Result = @.Result * @.Composite1 * @.TerritoryMod1
> END
> END
> END
> ELSE
> /* IF Payroll falls under 2 policy years */
> BEGIN
> DECLARE
> @.Territory2 AS int,
> @.TerritoryMod2 as decimal(10,4),
> @.WCRateID2 AS int,
> @.WCRate2 AS decimal(19,4),
> @.WCFactor2 AS varchar(50),
> @.Result1 AS decimal(19,4),
> @.Result2 AS decimal(19,4),
> @.NoDays1 AS int,
> @.NoDays2 AS int,
> @.PayrollLength AS int
>
> /* +++POLICY YEAR 1+++ */
> /* work code rate */
> SELECT @.WCRateID1 = WorkCodeRateID, @.WCRate1 = RateAmount, @.WCFactor1 => Factor from tblWorkCodeRate where CoverageEntryID = @.PolicyID1 and
> lkWorkCodeID = @.WorkCode
> IF (@.WCRateID1 is null)
> SELECT @.Result1 = 0
> ELSE
> BEGIN
> IF @.WCFactor1 = 'Rate/100'
> SELECT @.Result1 = @.WCRate1*0.01
> ELSE
> BEGIN
> IF @.WCFactor1='Rate/1000'
> SELECT @.Result1 = @.WCRate1*0.001
> ELSE
> SELECT @.Result1 = @.WCRate1
> END
> /* base */
> SELECT @.NoDays1= DATEDIFF(day,@.PayrollFrom,@.PolicyTo1)
> SELECT @.NoDays2= DATEDIFF(day,@.PayrollTo,@.PolicyFrom2)
> SELECT @.PayrollLength = @.NoDays1+@.NoDays2
> /* no of days for Policy Year 1= DateFrom - DateExpiration for Policy
> Year 1 */
> IF (@.CoverageType = 'Excess' OR @.CoverageType='GL')
> SELECT @.Result1 => @.Result1*((@.AmountEffective/@.PayrollLength)*@.NoDays1)
> IF (@.CoverageType = 'WC')
> BEGIN
> IF @.AmountCap =0
> SELECT @.Result1 => @.Result1*((@.AmountEffective/@.PayrollLength)*@.NoDays1)
> ELSE
> SELECT @.Result1 = @.Result1* ((@.AmountCap/@.PayrollLength)*@.NoDays1)
> END
> /* Territory */
> SELECT @.Territory1 = A.lkTerritoryID from tblPayrollHeader PH INNER
> JOIN tblAssignment A ON PH.AssignmentID = A.AssignmentID WHERE
> PH.PayrollHeaderID = @.PayrollHeaderID
> if (@.Territory1 is null)
> SELECT @.Result1 = @.Result1 * @.Composite1
> ELSE
> BEGIN
> SELECT @.TerritoryMod1= Modifier from tblTerritoryModifier WHERE
> lkTerritoryID = @.Territory1 and WorkCodeRateID = @.WCRateID1
> IF (@.TerritoryMod1 is NULL) OR (@.TerritoryMod1=0)
> SELECT @.Result1 = @.Result1 * @.Composite1
> ELSE
> SELECT @.Result1 = @.Result1 * @.Composite1 * @.TerritoryMod1
> END
>
> END
> /* +++POLICY YEAR 2+++ */
> /* work code rate */
> SELECT @.WCRateID2 = WorkCodeRateID, @.WCRate2 = RateAmount, @.WCFactor2 => Factor from tblWorkCodeRate where CoverageEntryID = @.PolicyID2 and
> lkWorkCodeID = @.WorkCode
> IF (@.WCRateID2 is null)
> SELECT @.Result2 = 0
> ELSE
> BEGIN
> IF @.WCFactor2 = 'Rate/100'
> SELECT @.Result2 = @.WCRate2*0.01
> ELSE
> BEGIN
> IF @.WCFactor2='Rate/1000'
> SELECT @.Result2 = @.WCRate2*0.001
> ELSE
> SELECT @.Result2 = @.WCRate2
> END
> /* base */
> IF (@.CoverageType = 'Excess' OR @.CoverageType='GL')
> SELECT @.Result2 => @.Result2*((@.AmountEffective/@.PayrollLength)*@.NoDays2)
> IF (@.CoverageType = 'WC')
> BEGIN
> IF @.AmountCap =0
> SELECT @.Result2 => @.Result2*((@.AmountEffective/@.PayrollLength)*@.NoDays2)
> ELSE
> SELECT @.Result2 = @.Result2* ((@.AmountCap/@.PayrollLength)*@.NoDays2)
> END
> /* Territory */
> SELECT @.Territory2 = A.lkTerritoryID from tblPayrollHeader PH INNER
> JOIN tblAssignment A ON PH.AssignmentID = A.AssignmentID WHERE
> PH.PayrollHeaderID = @.PayrollHeaderID
> if (@.Territory2 is null)
> SELECT @.Result2 = @.Result2 * @.Composite2
> ELSE
> BEGIN
> SELECT @.TerritoryMod2= Modifier from tblTerritoryModifier WHERE
> lkTerritoryID = @.Territory2 and WorkCodeRateID = @.WCRateID2
> IF (@.TerritoryMod2 is NULL) OR (@.TerritoryMod2=0)
> SELECT @.Result2 = @.Result2 * @.Composite2
> ELSE
> SELECT @.Result2 = @.Result2 * @.Composite2 * @.TerritoryMod2
> END
> END
> SELECT @.Result = @.Result1 + @.Result2
> END
> END
> return @.Result
>
> END
>sql