For many, the new SQL Server 2014 Cardinality Estimator (CE) will prove more helpful than even Hekaton or SSD caching. For others, the new CE may actually hurt performance. To ensure that applications run at peak performance after upgrading to SQL Server 2014, learn more about: *How, why, and when SQL Server uses statistics *When and where the new CE will be useful (or harmful) *How to quickly verify the differences between the legacy CE and the new CE for any query

1. Cardinality Estimates in SQL Server 2014
Thomas LaRock
Head Geek
Solarwinds
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2. Why Are You Here?
» You are thinking about migrating/upgrading to SQL 2014 at
some point
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3. Why Are You Here?
» You are thinking about migrating/upgrading to SQL 2014 at
some point
» You’ve been told to migrate to SQL 2014
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4. Why Are You Here?
» You are thinking about migrating/upgrading to SQL 2014 at
some point
» You’ve been told to migrate to SQL 2014
» You want to understand more about specific changes to
cardinality estimates
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5. © 2014 SOLARWINDS WORLDWIDE, LLC. ALL RIGHTS RESERVED.
A Little About Me…
@sqlrockstar
sqlrockstar@
thomaslarock.com
linkedin.com/in/sqlrockstar

6. solarwinds.com/products
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A Little About Solarwinds…
@headgeeks
lab.solarwinds.com
confio.com/events

7. » Why cardinality matters
» What’s new in SQL 2014
» See the new CE in action
» Questions
Agenda
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8. © 2014 SOLARWINDS WORLDWIDE, LLC. ALL RIGHTS RESERVED.
Cardinality: Why It Matters

9. How most people see SQL Server
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10. How most people see SQL Server
QUERY
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11. How most people see SQL Server
QUERY DATA
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12. What’s inside the box?
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13. What Happens When a Connection Is Made to
SQL Server
Connection
• Session ID
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14. What Happens When a Connection Is Made to
SQL Server
Connection
• Session ID
Request
• Query sent
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15. What Happens When a Request Is Sent To SQL
Server
Parse
Syntax
check;
reserved
keywords,
column and
table names
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16. What Happens When a Request Is Sent To SQL
Server
Parse
Syntax
check;
reserved
keywords,
column and
table names
Bind
Name
reservation,
type
derivation,
aggregates,
grouping
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17. What Happens When a Request Is Sent To SQL
Server
Parse
Syntax
check;
reserved
keywords,
column and
table names
Bind
Name
reservation,
type
derivation,
aggregates,
grouping
Optimize
Find “good
enough”
plan
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18. What Happens When a Request Is Sent To SQL
Server
Parse
Syntax
check;
reserved
keywords,
column and
table names
Bind
Name
reservation,
type
derivation,
aggregates,
grouping
Optimize
Find “good
enough”
plan
Execute
Storage
Engine
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19. What Happens When a Request Is Sent To SQL
Server
Parse
Syntax
check;
reserved
keywords,
column and
table names
Bind
Name
reservation,
type
derivation,
aggregates,
grouping
Optimize
Find “good
enough”
plan
Execute
Storage
Engine
Logical Engine
© 2014 SOLARWINDS WORLDWIDE, LLC. ALL RIGHTS RESERVED.

20. What Happens When a Request Is Sent To SQL
Server
Parse
Syntax
check;
reserved
keywords,
column and
table names
Bind
Name
reservation,
type
derivation,
aggregates,
grouping
Optimize
Find “good
enough”
plan
Execute
Storage
Engine
Logical Engine
© 2014 SOLARWINDS WORLDWIDE, LLC. ALL RIGHTS RESERVED.

21. What Happens When a Connection Is Made to
SQL Server
Connection
• Session ID
Request
• Query sent
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22. What Happens When a Connection Is Made to
SQL Server
Connection
• Session ID
Request
• Query sent
Optimize
• Optimization
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23. » Primary goal: To find plan with “least cost”
What Happens During Query Optimization in
SQL Server
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24. » Primary goal: To find plan with “least cost”
» Will stop when “good enough” plan is found
What Happens During Query Optimization in
SQL Server
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25. » Primary goal: To find plan with “least cost”
» Will stop when “good enough” plan is found
» Uses statistics(!) to estimate rows needed for
operators in the execution plan
What Happens During Query Optimization in
SQL Server
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26. » Primary goal: To find plan with “least cost”
» Will stop when “good enough” plan is found
» Uses statistics(!) to estimate rows needed for
operators in the execution plan
» The cost is an abstraction, no correlation to
performance (ie., CPU ticks)
What Happens During Query Optimization in
SQL Server
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27. » Primary goal: To find plan with “least cost”
» Will stop when “good enough” plan is found
» Uses statistics(!) to estimate rows needed for
operators in the execution plan
» The cost is an abstraction, no correlation to
performance (ie., CPU ticks)
What Happens During Query Optimization in
SQL Server
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28. Query Optimization Model
» Contents are a mystery
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29. Query Optimization Model
» Contents are a mystery
(except to Conor and his
team)
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30. Query Optimization Model
» Contents are a mystery
(except to Conor and his
team)
» You don’t need the details
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31. Query Optimization Model
» Contents are a mystery
(except to Conor and his
team)
» You don’t need the details
(no, you don’t)
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32. Query Optimization Model
» Contents are a mystery
(except to Conor and his
team)
» You don’t need the details
(no, you don’t)
» You need the bigger picture
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33. 1. Does plan already exist? In not, continue to next
step.
The bigger picture
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34. 1. Does plan already exist? In not, continue to next
step.
2. Is this a trivial plan? If not, continue.
The bigger picture
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35. 1. Does plan already exist? In not, continue to next
step.
2. Is this a trivial plan? If not, continue.
3. Apply simplification.
The bigger picture
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36. 1. Does plan already exist? In not, continue to next
step.
2. Is this a trivial plan? If not, continue.
3. Apply simplification.
4. Is this plan cheap enough? If not, continue.
The bigger picture
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37. 1. Does plan already exist? In not, continue to next
step.
2. Is this a trivial plan? If not, continue.
3. Apply simplification.
4. Is this plan cheap enough? If not, continue.
5. Start cost-based optimization
The bigger picture
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38. 1. Does plan already exist? In not, continue to next
step.
2. Is this a trivial plan? If not, continue.
3. Apply simplification.
4. Is this plan cheap enough? If not, continue.
5. Start cost-based optimization
The bigger picture
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39. » Explore basic rules
Cost-based optimization
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40. » Explore basic rules
» Does plan have a cost less than 0.2?
Cost-based optimization
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41. » Explore basic rules
» Does plan have a cost less than 0.2?
 Explore more rules, alternate join ordering. If the best plan is less than
1.0, use that plan. If not, but MAXDOP is > 0 and this is an SMP system
and the min cost > cost for parallelism, then use a parallel plan.
Compare the cost of parallel plan to best serial plan and pass the
cheaper of the plans along.
Cost-based optimization
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42. » Explore basic rules
» Does plan have a cost less than 0.2?
 Explore more rules, alternate join ordering. If the best plan is less than
1.0, use that plan. If not, but MAXDOP is > 0 and this is an SMP system
and the min cost > cost for parallelism, then use a parallel plan.
Compare the cost of parallel plan to best serial plan and pass the
cheaper of the plans along.
» Opt for the cheapest plan after a limited number of
explorations
Cost-based optimization
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43. Why This Matters
» Query optimizer contains
the Cardinality Estimator
(CE)
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44. Why This Matters
» Query optimizer contains
the Cardinality Estimator
(CE)
» The CE is dependent upon
statistics being current and
accurate
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45. Why This Matters
» Query optimizer contains
the Cardinality Estimator
(CE)
» The CE is dependent upon
statistics being current and
accurate
» If stats are missing,
incorrect, or invalid then
you are likely to get a sub-
optimal plan
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46. What’s inside the box?
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47. The CE is the DNA for your queries!
» DNA is what makes you
you
» DNA not easily seen or
understood
» CE is similar to DNA
» Tiny but BIG role
» Neither DNA nor CE are
trivial pieces of code
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48. What’s New In SQL Server 2014
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49. » There have been slight enhancements over the years
 Hotfixes, patches, trace flags
The CE has been unchanged since 7.0!
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50. » There have been slight enhancements over the years
 Hotfixes, patches, trace flags
» Goal for SQL2014 was not to avoid regression
The CE has been unchanged since 7.0!
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51. » There have been slight enhancements over the years
 Hotfixes, patches, trace flags
» Goal for SQL2014 was not to avoid regression
» It is a new CE
 Will work better for most queries
 May not work well for some
 Testing is vital!
The CE has been unchanged since 7.0!
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52. Legacy CE assumptions
Uniformity Independence
Containment Inclusion
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53. Legacy CE assumptions
Uniformity Independence
Containment Inclusion
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54. Legacy CE assumptions
Uniformity Independence
Containment Inclusion
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55. Legacy CE assumptions
Uniformity Independence
Containment Inclusion
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56. See the New CE in Action
DEMO
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57. Likely common scenarios
ASC/DESC Key Estimates
Multiple Column Dependency
Join Estimates
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58. Likely common scenarios
ASC/DESC Key Estimates
Multiple Column Dependency
Join Estimates
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59. Likely common scenarios
ASC/DESC Key Estimates
Multiple Column Dependency
Join Estimates
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60. New CE Changes That Require Action
If there are no
changes to
estimates or
the query
execution
plan…
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61. New CE Changes That Require Action
…but you are
seeing
degraded
performance
If there are no
changes to
estimates or
the query
execution
plan…
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62. New CE Changes That Require Action
…it’s not
related to the
new CE, but
general
performance
tuning may be
required
…but you are
seeing
degraded
performance
If there are no
changes to
estimates or
the query
execution
plan…
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63. New CE Changes That Require Action
No changes to
estimates but
the query
execution
plan
changed…
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64. New CE Changes That Require Action
…and you are
seeing
degraded
performance
No changes to
estimates but
the query
execution
plan
changed…
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65. New CE Changes That Require Action
…unlikely to
be related to
the new CE,
but tuning
may be
required
…and you are
seeing
degraded
performance
No changes to
estimates but
the query
execution
plan
changed…
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66. New CE Changes That Require Action
If there are
changes to
the estimates
regardless of
the query
execution
plan shape…
© 2014 SOLARWINDS WORLDWIDE, LLC. ALL RIGHTS RESERVED.

67. New CE Changes That Require Action
…and you are
seeing
degraded
performance
If there are
changes to
the estimates
regardless of
the query
execution
plan shape…
© 2014 SOLARWINDS WORLDWIDE, LLC. ALL RIGHTS RESERVED.

68. New CE Changes That Require Action
…action may
be necessary
if degradation
exceeds
workload
performance
SLAs
…and you are
seeing
degraded
performance
If there are
changes to
the estimates
regardless of
the query
execution
plan shape…
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69. Tips & Tricks
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70. Tips and Tricks
Auto Create/Update stats
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71. Tips and Tricks
Auto Create/Update stats
Database compatibility mode
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72. Tips and Tricks
Auto Create/Update stats
Database compatibility mode
Query trace flags
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73. Tips and Tricks
Auto Create/Update stats
Database compatibility mode
Query trace flags
XML showplan, xEvents
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74. » Why cardinality matters
» What’s new in SQL 2014
» See the new CE in action
» Questions
Agenda
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75. © 2014 SOLARWINDS WORLDWIDE, LLC. ALL RIGHTS RESERVED.
Thank You!
The SOLARWINDS and SOLARWINDS & Design marks are the exclusive
property of SolarWinds Worldwide, LLC, are registered with the U.S.
Patent and Trademark Office, and may be registered or pending
registration in other countries. All other SolarWinds trademarks, service
marks, and logos may be common law marks, registered or pending
registration in the United States or in other countries. All other
trademarks mentioned herein are used for identification purposes only
and may be or are trademarks or registered trademarks of their respective
companies.

76. Questions?
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77. » http://tinyurl.com/joe-sack-cardinality
» http://tinyurl.com/sql-2014-new-CE
» http://tinyurl.com/sql-2014-new-CE-p2
» http://tinyurl.com/CE-deep-dive-PWhite
» http://tinyurl.com/MSDN-CE-2014
Additional info
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