Scalar function with WHILE loop to inline function - sql-server

Question

Hi I have a view which is used in lots of search queries in my application.
The issue is application queries which use this view is is running very slow.I am investigating this and i found out a particular portion on the view definition which is making it slow.
create view Demoview AS
Select
p.Id as Id,
----------,
STUFF((SELECT ',' + [dbo].[OnlyAlphaNum](colDesc)
FROM dbo.ContactInfoDetails cd
WHERE pp.FormId = f.Id AND ppc.PageId = pp.Id
FOR XML PATH('')), 1, 1, '') AS PhoneNumber,
p.FirstName as Fname,
From
---
This is one of the column in the view.
The scalar function [OnlyAlphaNum] is making it slow,as it stops parallel execution of the query.
The function is as below;
CREATE FUNCTION [dbo].[OnlyAlphaNum]
(
#String VARCHAR(MAX)
)
RETURNS VARCHAR(MAX)
WITH SCHEMABINDING
AS
BEGIN
WHILE PATINDEX('%[^A-Z0-9]%', #String) > 0
SET #String = STUFF(#String, PATINDEX('%[^A-Z0-9]%', #String), 1, '')
RETURN #String
END
How can i convert it into an inline function.?
I tried with CASE ,but not successful.I have read that CTE is a good option.
Any idea how to tackle this problem.?

Answer 1

I already did this; you can read more about it here.
The function:
CREATE FUNCTION dbo.alphaNumericOnly8K(#pString varchar(8000))
RETURNS TABLE WITH SCHEMABINDING AS RETURN
/****************************************************************************************
Purpose:
Given a varchar(8000) string or smaller, this function strips all but the alphanumeric
characters that exist in #pString.
Compatibility:
SQL Server 2008+, Azure SQL Database, Azure SQL Data Warehouse & Parallel Data Warehouse
Parameters:
#pString = varchar(8000); Input string to be cleaned
Returns:
AlphaNumericOnly - varchar(8000)
Syntax:
--===== Autonomous
SELECT ca.AlphaNumericOnly
FROM dbo.AlphaNumericOnly(#pString) ca;
--===== CROSS APPLY example
SELECT ca.AlphaNumericOnly
FROM dbo.SomeTable st
CROSS APPLY dbo.AlphaNumericOnly(st.SomeVarcharCol) ca;
Programmer's Notes:
1. Based on Jeff Moden/Eirikur Eiriksson's DigitsOnlyEE function. For more details see:
http://www.sqlservercentral.com/Forums/Topic1585850-391-2.aspx#bm1629360
2. This is an iTVF (Inline Table Valued Function) that performs the same task as a
scalar user defined function (UDF) accept that it requires the APPLY table operator.
Note the usage examples below and see this article for more details:
http://www.sqlservercentral.com/articles/T-SQL/91724/
The function will be slightly more complicated to use than a scalar UDF but will yeild
much better performance. For example - unlike a scalar UDF, this function does not
restrict the query optimizer's ability generate a parallel query plan. Initial testing
showed that the function generally gets a
3. AlphaNumericOnly runs 2-4 times faster when using make_parallel() (provided that you
have two or more logical CPU's and MAXDOP is not set to 1 on your SQL Instance).
4. This is an iTVF (Inline Table Valued Function) that will be used as an iSF (Inline
Scalar Function) in that it returns a single value in the returned table and should
normally be used in the FROM clause as with any other iTVF.
5. CHECKSUM returns an INT and will return the exact number given if given an INT to
begin with. It's also faster than a CAST or CONVERT and is used as a performance
enhancer by changing the bigint of ROW_NUMBER() to a more appropriately sized INT.
6. Another performance enhancement is using a WHERE clause calculation to prevent
the relatively expensive XML PATH concatentation of empty strings normally
determined by a CASE statement in the XML "loop".
7. Note that AlphaNumericOnly returns an nvarchar(max) value. If you are returning small
numbers consider casting or converting yout values to a numeric data type if you are
inserting the return value into a new table or using it for joins or comparison
purposes.
8. AlphaNumericOnly is deterministic; for more about deterministic and nondeterministic
functions see https://msdn.microsoft.com/en-us/library/ms178091.aspx
Usage Examples:
--===== 1. Basic use against a literal
SELECT ao.AlphaNumericOnly
FROM samd.alphaNumericOnly8K('xxx123abc999!!!') ao;
--===== 2. Against a table
DECLARE #sampleTxt TABLE (txtID int identity, txt varchar(100));
INSERT #sampleTxt(txt) VALUES ('!!!A555A!!!'),(NULL),('AAA.999');
SELECT txtID, OldTxt = txt, AlphaNumericOnly
FROM #sampleTxt st
CROSS APPLY samd.alphaNumericOnly8K(st.txt);
---------------------------------------------------------------------------------------
Revision History:
Rev 00 - 20150526 - Inital Creation - Alan Burstein
Rev 00 - 20150526 - 3rd line in WHERE clause to correct something that was missed
- Eirikur Eiriksson
Rev 01 - 20180624 - ADDED ORDER BY N; now performing CHECKSUM conversion to INT inside
the final cte (digitsonly) so that ORDER BY N does not get sorted.
****************************************************************************************/
WITH
E1(N) AS
(
SELECT N
FROM (VALUES (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL))x(N)
),
iTally(N) AS
(
SELECT TOP (LEN(ISNULL(#pString,CHAR(32)))) ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
FROM E1 a CROSS JOIN E1 b CROSS JOIN E1 c CROSS JOIN E1 d
)
SELECT AlphaNumericOnly =
(
SELECT SUBSTRING(#pString,CHECKSUM(N),1)
FROM iTally
WHERE
((ASCII(SUBSTRING(#pString,CHECKSUM(N),1)) - 48) & 0x7FFF) < 10
OR ((ASCII(SUBSTRING(#pString,CHECKSUM(N),1)) - 65) & 0x7FFF) < 26
OR ((ASCII(SUBSTRING(#pString,CHECKSUM(N),1)) - 97) & 0x7FFF) < 26
ORDER BY N
FOR XML PATH('')
);
Note the examples in the code comments:
--===== 1. Basic use against a literal
SELECT ao.AlphaNumericOnly
FROM samd.alphaNumericOnly8K('xxx123abc999!!!') ao;
--===== 2. Against a table
DECLARE #sampleTxt TABLE (txtID int identity, txt varchar(100));
INSERT #sampleTxt(txt) VALUES ('!!!A555A!!!'),(NULL),('AAA.999');
SELECT txtID, OldTxt = txt, AlphaNumericOnly
FROM #sampleTxt st
CROSS APPLY samd.alphaNumericOnly8K(st.txt);
Returns:
AlphaNumericOnly
-------------------
xxx123abc999
txtID OldTxt AlphaNumericOnly
----------- ------------- -----------------
1 !!!A555A!!! A555A
2 NULL NULL
3 AAA.999 AAA999
It's the fastest of it's kind. It runs extra fast with a parallel execution plan. To force a parallel execution plan, grab a copy of make_parallel by Adam Machanic. Then you would run it like this:
--===== 1. Basic use against a literal
SELECT ao.AlphaNumericOnly
FROM dbo.alphaNumericOnly8K('xxx123abc999!!!') ao
CROSS APPLY dbo.make_parallel();
--===== 2. Against a table
DECLARE #sampleTxt TABLE (txtID int identity, txt varchar(100));
INSERT #sampleTxt(txt) VALUES ('!!!A555A!!!'),(NULL),('AAA.999');
SELECT txtID, OldTxt = txt, AlphaNumericOnly
FROM #sampleTxt st
CROSS APPLY dbo.alphaNumericOnly8K(st.txt)
CROSS APPLY dbo.make_parallel();

Answer 2

Surely there is scope to improve this. test it out.
;WITH CTE AS (
SELECT (CASE WHEN PATINDEX('%[^A-Z0-9]%', D.Name) > 0
THEN STUFF(D.Name, PATINDEX('%[^A-Z0-9]%', D.Name), 1, '')
ELSE D.NAME
END ) NameString
FROM #dept D
UNION ALL
SELECT STUFF(C.NameString, PATINDEX('%[^A-Z0-9]%', C.NameString), 1, '')
FROM CTE C
WHERE PATINDEX('%[^A-Z0-9]%', C.NameString) > 0
)
Select STUFF((SELECT ',' + E.NameString from CTE E
WHERE PATINDEX('%[^A-Z0-9]%', E.NameString) = 0
FOR XML PATH('')), 1, 1, '') AS NAME