Speeding up this query? Currently it takes 4 seconds on 100K rows - sql

Question

This is my main query:
exec sp_executesql N'set arithabort off;set transaction isolation level read uncommitted;Select COUNT(*) From ( Select ROW_NUMBER() OVER
(Order By Case When d.OldInstrumentID IS NULL THEN d.LastStatusChangedDateTime Else d.RecordingDateTime End desc ) peta_rn,
d.DocumentID
From Documents d
Inner Join Users u on d.UserID = u.UserID Inner Join IGroupes ig on ig.IGroupID = d.IGroupID
Inner Join ITypes it on it.ITypeID = d.ITypeID Where 1=1 ANd dbo.DoesNameExist(d.DocumentID, #0, #1, #2, #3) = 1 And (CreatedByAccountID = #4
Or DocumentStatusID = #5
Or DocumentStatusID = #6 ) )
v',N'#0 int,#1 varchar(4000),#2 varchar(4000),#3 nvarchar(4000),#4 int,#5 int,#6 int',#0=-999,#1='K',#2='Miller',
#3=NULL,#4=44,#5=5,#6=9
and this is my scalar function which is the culprit:
ALTER FUNCTION [dbo].[DoesNameExist]
(
#DocumentID int,
#PartyTypeID int = 0,
#FirstName varchar(30),
#LastName varchar(30),
#Business varchar(100)
)
RETURNS bit
AS
BEGIN
Declare #Found bit = 0
Set #FirstName = IsNull(#FirstName,'')
Set #LastName = IsNull(#LastName,'')
Set #Business = IsNull(#Business,'')
Select Top 1 #Found = 1
From DocumentNames
Where DocumentID = #DocumentID
And
Lower(IsNull(FirstName,'')) Like
Case When #FirstName = '' Then Lower(IsNull(FirstName,'')) + '%'
Else Lower(#FirstName) + '%' End
And
Lower(IsNull(LastName,'')) Like
Case When #LastName = '' Then Lower(IsNull(LastName,'')) + '%'
Else Lower(#LastName) + '%' End
And
Lower(IsNull(Business,'')) Like
Case When #Business = '' Then Lower(IsNull(Business,'')) + '%'
Else Lower(#Business) + '%' End
And
PartyTypeID = Case When #PartyTypeID IS NULL OR #PartyTypeID <= 0 Then PartyTypeID Else #PartyTypeID End
Return #Found
END
Basically one document has multiple DocumentNames and when the user types something in LastName or FirstName, I want to bring the count of all documents which have those matching names. Please note, I am querying on Documents table and then joining to DocumentNames. This is necessary.
Note: Indexes are created on all search columns which include FirstName, LastName etc.
Thanks!

Answer 1

First, check Execution plan. How may times IsNULL() is getting used?Check estimated and actual time taken for all IsNULL(). If it is more, use a subquery where you can just calculate IsNULL() and supply to your query.
I do not have your Exceution plan. You can also try this aswell :
ALTER FUNCTION [dbo].[DoesNameExist]
(
#DocumentID int,
#PartyTypeID int = 0,
#FirstName varchar(30),
#LastName varchar(30),
#Business varchar(100)
)
RETURNS bit
AS
BEGIN
Declare #Found bit = 0
Select Top 1 #Found = 1
From DocumentNames
Where DocumentID = #DocumentID
And
Lower(IsNull(FirstName,'')) Like COALESCE(#FirstName,firstname,'')+'%'
And
Lower(IsNull(LastName,'')) Like COALESCE(#LastName,LastName,'')+'%'
And
Lower(IsNull(Business,'')) Like COALESCE(#Business,Business,'')+'%'
And
PartyTypeID = Case When #PartyTypeID IS NULL OR #PartyTypeID <= 0 Then PartyTypeID Else #PartyTypeID End
Return #Found
END
Also if you are ok to discard this UDF, using this directly in your statement with EXISTS clause should do the trick.
Select COUNT(*) From ( Select ROW_NUMBER() OVER
(Order By Case When d.OldInstrumentID IS NULL THEN d.LastStatusChangedDateTime Else d.RecordingDateTime End desc ) peta_rn,
d.DocumentID
From Documents d
Inner Join Users u on d.UserID = u.UserID Inner Join IGroupes ig on ig.IGroupID = d.IGroupID
Inner Join ITypes it on it.ITypeID = d.ITypeID Where 1=1
ANd EXISTS (
Select 1
From DocumentNames
Where DocumentID = d.DocumentID
And
Lower(IsNull(FirstName,'')) Like COALESCE(#1,lower(firstname),'')+'%'
And
Lower(IsNull(LastName,'')) Like COALESCE(#2,lower(LastName),'')+'%'
And
Lower(IsNull(Business,'')) Like COALESCE(#3,lower(Business),'')+'%'
And
PartyTypeID = Case When #0 IS NULL OR #0 <= 0 Then PartyTypeID Else #0 End
)
Or DocumentStatusID = #5
Or DocumentStatusID = #6 ) )
v',N'#0 int,#1 varchar(4000),#2 varchar(4000),#3 nvarchar(4000),#4 int,#5 int,#6 int',#0=-999,#1='K',#2='Miller',
#3=NULL,#4=44,#5=5,#6=9