1. The Key to the Database Engine
Execution Plan Essentials
The Key to the Database Engine
Eugene Meidinger, BI Consultant, All Lines Technology

2. BI Consultant, All Lines Technology
Went from SQL Newbie to SQL Pro in the last 6 years. Experience with T-SQL, SSRS and Power BI
Pluralsight Author
Author of video training on Pluralsight. Currently focusing on Power BI content
Eugene Meidinger
BI Consultant, All Lines Technology
Pittsburgh PUG co-leader
Help lead the Pittsburgh Power BI User Group.
/eugenemeidinger
@sqlgene

3. Agenda This is an introductory session on execution plans.
What are execution plans?
How do you read them?
What do the operators mean?
What’s new since SQL Server 2012?
Demos, Demos, Demos

4. What are Execution Plans?
An execution plan represents the steps the database engine takes.
When the Database Engine processes a query, it creates a series of steps
You can think of this like a recipe, or driving directions
Execution plans give you insight into the choices the engine made
Some plans can be wildly inefficient (human error, bad statistics, etc.)
Execution plans are cached for future runs

5. Database Engines are like GPS Devices
You use a GPS device to tell you how to get from point A to point B as efficiently as possible
A driving plan is a series of steps or operations (turn left, turn right, go straight, etc.)
A driving plan has a set of costs (miles, gas, time, tolls, etc.)
A GPS device usually provides multiple options, with different costs
Part of the Database Engine works to figure out how to get data from disk to the client as efficiently as possible
An execution plan is a series of steps or operations (Index scan, filter data, SELECT)
An execution plan has a set of costs (IO, CPU, RAM, time)
The database engine will produce multiple potential execution plans

6. How Do We View Execution Plans?
We have three different options.
Go to Query
Click Include Actual Execution Plan
Or, press Ctrl + M
Or, click the execution plan icon on the toolbar

7. What Does a Plan Look Like?

8. How to Read an Execution Plan
It’s a roadmap for your data.
Read from right to left and top to bottom
Imagine everyone driving towards the SELECT
Icons represent operators
Thinks of operators as turns on your road trip
Operators have costs below them
Arrow represent data flow
Think of them as traffic indicators
Bigger arrows mean more rows
Hover over icons and arrows for more detail

9. Missing Indexes
The database engine will suggest missing indexes.

10. Types of Operators There are a few broad categories. Gathering Data
Joining Data
Manipulating Data
MISC

11. Gathering Data This is the starting point for any execution plan.
Table scan
Clustered index scan
Clustered index seek
Nonclustered index scan
Nonclustered index seek
RID lookup
Key lookup

12. SARGability When can you use your indexes?
SARGability (Search Argument) means your query can use your indexes.
Imagine if I asked for all the Smiths from the phonebook. That’s SARGable.
Imagine if I asked for all Last names with an R. That’s not SARGable.
Manipulating a column in your where clause can break SARGability.

13. Joining Data There are three types of joins Nested Loop Join
Ideal when one dataset is small
Merge Join
Ideal when both datasets are sorted
Hash Join
Ideal for large datasets
Memory intensive!!!

14. Manipulating Data
There are a lot of ways to manipulate data. These are a few.
Compute Scalar
Filter
Sort
Top

15. What’s new? A lot has changed since 2008 R2. Compare Showplan
Cardinality Estimator
Row Level Security
Live Query Statistics
Query Store
Adaptive Query Plans

16. Execution Plans
Demo

17. Learn more from Eugene Meidinger
@sqlgene