1. to my madness! Janis Griffin Senior DBA, Confio Software
Tuna Helper Proven Process for SQL Tuning Janis Griffin Senior DBA, Confio Software
Query Tuning Get it Right the First Time Janis Griffin Senior DBA, Confio Software
Looney Tuner?
No, there IS a method
to my madness! Janis Griffin Senior DBA, Confio Software 1 1

2. Who Am I? Senior DBA for Confio Software
Twitter
Current – 24+ Years in SQL Server & Oracle
DBA and Developer
Specialize in Performance Tuning
Review Database Performance for Customers and Prospects
Common Thread – Paralyzed by Tuning

3. Agenda Challenges Of Tuning Utilize Response Time Analysis (RTA)
Who should tune
Which SQLs to tune
Utilize Response Time Analysis (RTA)
Gather Details about SQL
Example Query Execution Plans
Use SQL or Query Diagramming
Who registered yesterday for Tuning Class
Lookup paycheck information
Check order status
Monitor – Make sure it stays tuned

4. Challenges Of Tuning SQL Tuning is Hard
Requires Expertise in Many Areas
Technical – Plan, Data Access, SQL Design
Business – What is the Purpose of SQL?
Tuning Takes Time
Large Number of SQL Statements
Each Statement is Different
Low Priority in Some Companies
Vendor Applications
Focus on Hardware or System Issues
Never Ending

5. Who Should Tune Developers? DBA? Need a team approach
Developing applications is very difficult
Typically focused on functionality
Not much time left to tune SQL
Don’t get enough practice or simply don’t know
SQL runs differently in Production versus Dev/Test
DBA?
Do not know the code like developers do
Focus on “Keep the Lights On”
Very complex environment
Need a team approach

6. Which SQL to Tune User / Batch Job Complaints
Known Poorly Performing SQL
Queries Performing Most I/O (LIO, PIO)
Table or Index Scans
Queries Consuming CPU
Highest Response Times (Ignite8)
SELECT sql_handle, statement_start_offset, statement_end_offset, plan_handle, execution_count, total_logical_reads, total_physical_reads, total_elapsed_time, st.text
FROM sys.dm_exec_query_stats AS qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) AS st
ORDER BY total_elapsed_time DESC

7. Response Time Analysis (RTA)
Focus on Response Time
Understand the total time a Query spends in Database
Measure time while Query executes
SQL Server helps by providing Wait Types 7

8. Wait Time Tables (SQL 2005/8)
sysprocesses
loginame
hostname
programname
spid
dbid
waittype
waittime
Lastwaittype
waitresource
sql_handle
stmt_start
stmt_end
cmd
dm_exec_sessions
login_time
login_name
host_name
program_name
session_id
dm_exec_requests
start_time
status
sql_handle
plan_handle
start/stop offset
database_id
user_id
blocking_session
wait_type
wait_time
dm_os_wait_stats
wait_type
waiting_tasks_count
wait_time_ms
dm_exec_query_stats
execution_count
total_logical_writes
total_physical_reads
total_logical_reads
dm_exec_query_plan
query_plan
dm_exec_sql_text
text

9. Problems with DMVs Can give an overall performance view
Can find costly queries and other problems.
Contents are from instance startup
No way to tie some information to a timeframe.
Are these Query stats from today or last week?
Need to sample data periodically
Be able to go back to 3:00 pm yesterday when problem occurred.
How often and when does this query execute?

10. Base Monitoring Query
INSERT INTO SessionWaitInfo SELECT r.session_id, r.sql_handle, r.statement_start_offset, r.statement_end_offset, r.plan_handle, r.database_id, r.blocking_session_id, r.wait_type, r.query_hash, s.host_name, s.program_name, s.host_process_id, s.login_name, CURRENT_TIMESTAMP cdt FROM sys.dm_exec_requests r INNER JOIN sys.dm_exec_sessions s ON s.session_id = r.session_id WHERE r.status <> 'background' AND r.command <> 'AWAITING COMMAND' AND s.session_id > 50 AND s.session_id <>

11. RTA Tuning Data

12. RTA Benefits
Before After

13. Wait Time Scenario Which scenario is worse? SQL Statement 1
Executed 1000 times
Caused 10 minutes of wait time for end user
Waited 90% of time on “PAGEIOLATCH_SH”
SQL Statement 2
Executed 1 time
Waited 90% on “LCK_M_X”

14. Gather Metrics Get baseline metrics Collect Wait Type Information
How long does it take now
What is acceptable (10 sec, 2 min, 1 hour)
Collect Wait Type Information
Locking / Blocking (LCK)
I/O problem (PAGEIOLATCH)
Latch contention (LATCH)
Network slowdown (NETWORK)
May be multiple issues
All have different resolutions

15. Get Execution Plan SQL Server Management Studio
Estimated Execution Plan - can be wrong for many reasons
Actual Execution Plan – must execute query, can be dangerous in production and also wrong in test
SQL Server Profiler Tracing
Event to collect:
Performance: Execution Plan (2000) , Showplan XML (2005/8)
Works when you know a problem will occur
DM_EXEC_QUERY_PLAN
Real execution plan of executed query

16. DM_EXEC_QUERY_PLAN

17. Review Table Information
Table Definition
Where does it physically reside
Large columns?
Data Profile Task / Viewer – Integration Services
Existing Indexes
Names of all existing indexes
Columns those indexes contain
Statistic Gathering & Rebuild Schedules

18. Case Studies SQL Diagramming Who registered yesterday for Tuning Class
Lookup paycheck information
Check order status

19. SQL Statement 1 Who registered yesterday for SQL Tuning
SELECT s.fname, s.lname, r.signup_date
FROM student s
INNER JOIN registration r ON s.student_id = r.student_id
INNER JOIN class c ON r.class_id = c.class_id
WHERE c.name = 'SQL TUNING'
AND r.signup_date
AND r.cancelled = 'N'
Execution Stats – 17,910 Logical Reads
Execution Time – 1:30 to execute
Wait Types – Waits 90% on PAGEIOLATCH_SH

20. Relationship Diagram

21. Execution Plan Recommendation from SSMS CREATE NONCLUSTERED INDEX
[<Name of Missing Index>]
ON [dbo].[registration] ([cancelled],[signup_date])
INCLUDE ([student_id],[class_id])
17,910 Logical Reads

22. Database Tuning Advisor
2 Indexes & 4 Additional Statistics 22

23. SQL Diagramming Great Book “SQL Tuning” by Dan Tow registration
Great book that teaches SQL Diagramming
registration
.04 5 30 1 1
student
class
.001
select count(1) from registration where cancelled = 'N'
and signup_date between ' :00' and ' :00'
64,112 / 1,740,145 =
select count(1) from class where name = 'SQL TUNING'
2 / 1,267 = .001

24. New Execution Plan Execution Stats – 17,152 Logical Reads
CREATE INDEX cl_name ON class(name)
Execution Stats – 17,152 Logical Reads
Why would an Index Scan still occur on REGISTRATION?

25. Gather – Existing Indexes

26. New Execution Plan Execution Stats – 266 Logical Reads
CREATE INDEX reg_alt ON registration(class_id)
Execution Stats – 266 Logical Reads

27. Better Execution Plan Execution Stats – 20 Logical Reads
CREATE INDEX reg_alt ON registration(class_id)
INCLUDE (signup_date, cancelled)
Execution Stats – 20 Logical Reads
Metric – Takes 0:00 (sub-second) to execute 27

28. Alternative from SSMS
CREATE INDEX reg_can ON registration(cancelled, signup_date)
INCLUDE (class_id, student_id)
CREATE NONCLUSTERED INDEX
[<Name of Missing Index>]
ON [dbo].[registration]
([class_id],[cancelled],[signup_date])
INCLUDE ([student_id])

29. SQL Statement 2 Current paychecks for specific employees
SELECT e.first_name, e.last_name, l.description
FROM emp e
INNER JOIN loc l ON e.loc_id = l.loc_id
WHERE (e.first_name OR e.last_name
AND EXISTS (
SELECT 1
FROM wage_pmt w
WHERE w.emp_id = e.emp_id
AND w.pay_date>= DATEADD(day,-31,CURRENT_TIMESTAMP) )
Execution Stats – 64,206 Logical Reads

30. Relationship Diagram

31. Execution Plan

32. SQL Diagramming wage_pmt emp loc select count(1) from wage_pmt
.02 90 1
emp
.0005
.0009
1000 1
loc
select count(1) from wage_pmt
where pay_date >= DATEADD(day,-31,CURRENT_TIMESTAMP)
40,760 / 1,915,088 = .02
select top 5 first_name, count(1) from emp
group by first_name order by 2 desc
12 / 23,798 = – first_name
22 / 23,789 = – last_name

33. New Execution Plan CREATE INDEX ix1_last_name ON emp(last_name)
CREATE INDEX ix2_fname ON emp(first_name)

34. Which Index? SSMS Recommendation
CREATE INDEX wp_pay_date ON wage_pmt(pay_date)
INCLUDE (emp_id)
50,000 Logical Reads
or…
Better Option
CREATE INDEX wp_emp_pd ON wage_pmt(emp_id, pay_date)
46 Logical Reads

35. New Execution Plan
CREATE INDEX wp_emp_pd ON wage_pmt(emp_id, pay_date)

36. SQL Statement 3 Lookup order status for caller
SELECT o.OrderID, c.LastName, p.ProductID, p.Description,
sd.ActualShipDate, sd.ShipStatus, sd.ExpectedShipDate
FROM [Order] o
INNER JOIN Item i ON i.OrderID = o.OrderID
INNER JOIN Customer c ON c.CustomerID = o.CustomerID
INNER JOIN ShipmentDetails sd ON sd.ShipmentID = i.ShipmentID
LEFT OUTER JOIN Product p ON p.ProductID = i.ProductID
LEFT OUTER JOIN Address a ON a.AddressID = sd.AddressID
WHERE c.LastName LIKE + '%'
--AND c.FirstName LIKE + '%'
AND o.OrderDate >= DATEADD(day, -30, CURRENT_TIMESTAMP)
AND sd.ShipStatus <> 'C'
Execution Stats – 10,159 Logical Reads

37. Database Diagram

38. Execution Plan

39. SQL Diagramming o i c sd p a
.08
.005 i c
.03 sd p a
SELECT COUNT(1)*1.0/(SELECT COUNT(1) FROM Customer) FROM Customer
WHERE LastName LIKE 'SMI%'
.03
SELECT COUNT(1)*1.0/(SELECT COUNT(1) FROM [Order]) FROM [Order]
WHERE OrderDate >= DATEADD(day, -30, CURRENT_TIMESTAMP)
.08
WHERE OrderStatus <> 'C'
.005
-- Combined

40. Data Skew Problems Only 0.5% of rows are <> ‘C’
SELECT OrderStatus, COUNT(1)
FROM [Order]
GROUP BY OrderStatus
Only 0.5% of rows are <> ‘C’
How about changing the query?
AND o.OrderStatus = 'I'
Add an Index on ShipStatus

41. New Execution Plan Execution Stats – 3,052 Logical Reads
CREATE INDEX IX2_OrderStatus ON [Order] (OrderStatus)
INCLUDE (OrderID,CustomerID)
Execution Stats – 3,052 Logical Reads

42. Monitor Monitor the improvement Monitor for next tuning opportunity
Be able to prove that tuning made a difference
Take new metric measurements
Compare them to initial readings
Brag about the improvements – no one else will
Monitor for next tuning opportunity
Tuning is iterative
There is always room for improvement
Make sure you tune things that make a difference
Shameless Product Pitch - Ignite

43. Takeaway Points Tuning Queries gives more “bang for the buck”
Make sure you are tuning the correct query
Use Wait Types and Response Time Analysis
Locking problems may not be a Query Tuning issue
Wait types tell you where to start
Use “Real Execution Plans”
Get plan_handle from DM_EXEC_REQUESTS
Pass plan_handle to DM_EXEC_QUERY_PLAN()
SQL Diagramming
Query Tuner Tools can mislead you
Monitor For Next Tuning Opportunity

44. Confio Software Wait-Based Performance Tools Igniter Suite
Ignite for SQL Server, Oracle, DB2, Sybase
Helps show which SQL to tune
Based in Colorado, worldwide customers
Free trial at