1. The Ins and Outs of Partitioned Tables
SQL Saturday Houston
Brian Dudley
Senior Solution Architect
Perficient, Inc.

2. Large Databases
What is large?
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3. Large Databases What is large? Issues with large databases Backups
Contention
Maintenance
Loading
Archiving
Index rebuilds
Performance
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4. https://en.wikipedia.org/wiki/Partition_(database)
What is Partitioning?
“A partition is a division of a logical database or its constituent elements into distinct independent parts. Database partitioning is normally done for manageability, performance or availability reasons, as for load balancing.“
Criteria
Range – only one supported by SQL Server
List
Hash
Partitioning Methods
Vertical – splitting out columns
Horizontal – dividing by row
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5. Benefits of Partitioning
Partitioning is largely handled transparently
Ability to move large amounts of data in or out of a table with metadata operation.
Ease of maintenance
Rebuild indexes by partition
Piecemeal backup and restore at the table level
Tuning of tables
Location of data
Compression by partition
Performance gains
Partition elimination
Better joins across partitioned tables
Increased options for parallel operation
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6. Caveats Partitioning is an Enterprise Version feature
Use Developer Edition for testing and learning
Partitioning is an involved topic.
Test your assumptions
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7. Thank You Sponsors!
Visit the Sponsor tables to enter their end of day raffles.
Turn in your completed Event Evaluation form at the end of the day in the Registration area to be entered in additional drawings.
Want more free training? Check out the Houston Area SQL Server User Group which meets on the 2nd Tuesday of each month. Details at
5/14/2016

8. Partitioning Mechanics
Determine tables to partition
What pain point does it address?
What is the strategy?
Decide on Partition Key
Data Type
Range
Should be commonly used in queries
Define Partition Function
Develop Partition Scheme
Create Tables and Indexes on Partition
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9. Partition Function
Create Partition Function <name> (<input parameter data type>)
As Range [Left|Right] For Values (<list>)
Input Parameter Data Type
Most types can be used
Date, Time, Integer Date Key, Int are Common
Enter sorted or it will be done
Consider collation
Watch formatting of Date/Time values
Value List
Can use variables and functions
Cannot use SQL Expressions
0 to 14,999 entries
Lends itself well to being automated
No duplicate values
Null can be specified, but should be avoided. Always sorts first.
$Partition.<function name>(<value>)
tells on which partition a row will be placed
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10. Left or Right Illustrated
Create Partition Function PF_Left(int) As Range Left For Values(10, 20, 30, 40) Create Partition Function PF_LeftEquiv(int) As Range Right For Values(11, 21, 31, 41) Create Partition Function PF_Right(int) As Range Right For Values(10, 20, 30, 40) Create Partition Function PF_RightEquiv(int) As Range Left For Values(9, 19, 29, 39)
Left
<-…10
11…20
21…30
31…40
41…->
Right
<-…9
10…19
20…29
31…39
40…->
Date Example – Right or Left?
< Dec 31
2016 Jan
1…31
2016 Feb
1…29
2016 Mar
1…31
2016 Apr 1
->
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11. Partition Scheme File Group List Design Decision
Create Partition Scheme <name> As Partition <partition function> To (<file group list>)
Create Partition Scheme <name> As Partition <partition function> All To (<file group>)
File Group List
Number of Boundary Values + 1
Can specify “Next Used”
Design Decision
Single File group
File group Per Partition
Older data on slower media
Mix of Read only and Writeable
Rotating List to “Stripe” the data
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12. Partition a Table
Table must have a column that serves as the Partition Key
Must be identical to the function parameter
Can be a Persisted Computed Column
e.g. Composite key
Include On <Partition Scheme>(<key>)
Many Tables can use the same Scheme
Partition existing table with Clustered Index
SSMS has Wizards
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13. Indexes on Partitioned Tables
Aligned – uses the same partition scheme as the table.
Default behavior for an index is to be aligned.
Partition key is added to the index if it is not already specified.
Has an impact on unique indexes.
All active indexes must be aligned when swapping partitions.
Logically, each partition has its own index.
Non-aligned – explicitly created on its own File Group or Partition
Can give better performance for searches that cross partitions.
Have to be disabled in order to swap data.
Factor in the cost of rebuilding.

14. Inspecting with System Views
sys.Partition_Functions
sys.Partition_Range_Values
Left Join because of the extra partition
Add 1 to boundary_id for Range Right
sys.Partition_Schemes
sys.Indexes
sys.Data_Spaces
Holds both Partition Schemes and File Groups
Type and Type Description fields
sys.Destination_Data_Spaces
sys.FileGroups
sys.Partitions
Every table and index has an entry
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15. Switching Partitions Major benefit of Partitioned Tables Requirements
Able to move a large amount of data as a metadata operation
Load new data
Remove old data for archive or truncation
Requirements
Two tables are required, at least one is partitioned
Partition schemes must be compatible
Tables must match in column name, data type, and order
Indexes must all be aligned and must match
Destination partition must exist and be empty
Must acquire a schema lock
Can cause time outs
SSMS has Wizards
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16. Switch Illustrated
Alter Table Right Switch Partition 3 To StagingTable Partition 3
Right
<-…9
10…19
20…29
31…39
40…->
Data is moved with a metadata operation
StagingTable
<-…9
10…19
20…29
31…39
40…->

17. Split and Merge Used to maintain partition functions and schemes
All Partition Schemes using a Partition Function are changed.
All Tables on a Partition Scheme are changed.
Can cause data movement
Best case is to only effect empty partitions
Sliding Window use case uses both splitting and merging
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18. Merge Illustrated Alter Partition Function PF_Right() Merge Range(10)
<-…9
10…19
20…29
31…39
40…->
Alter Partition Function PF_Right() Merge Range(10)
This file group is removed.
Any data is moved.
10…19
Right
<-…19
20…29
31…39
40…->

19. Split Illustrated
Right
<-…9
10…19
20…29
31…39
40…->
Alter Partition Scheme PS_Right Next Used FG1 Alter Partition Function PF_Right() Split Range(50)
FG1
Scheme knows what File Group to use.
Data will be moved if necessary.
Right
<-…9
10…19
20…29
31…39
40…49
50…->

20. ETL – Incremental Load
Scenario: Data mart is refreshed monthly with new transactional data.
Use split to create a new partition on a designated Next File Group.
Partitions can also be created in advance.
Create a non-partitioned staging table matching the target structure.
File group matches the new partition
Populate the staging table with a bulk copy
Add all necessary indexes.
Add a Check constraint.
Swap data into target table.
Update statistics on the target table.

21. ETL – Sliding Window
Scenario: Maintain a fixed number of months of data.
Create a non-partitioned archive table with necessary indexes.
File group matches the last partition.
Swap out the last partition.
Data can be truncated or archived.
Merge the now empty partition.
Use split to create a new partition on a designated Next File Group.
Create a non-partitioned staging table matching the target table.
File group matches the new partition
Populate the staging table with a bulk copy
Add all necessary indexes.
Add a Check constraint.
Swap data into target table.
Update statistics on the target table.

22. Odds and Ends Partition Elimination Identity Columns Transactions
Shows in the actual plan detail
Identity Columns
Enforcing Uniqueness
Ident_Current()
Transactions

23. References Microsoft Whitepapers Brent Ozar Books Online
“Partitioned Table and Index Strategies Using SQL Server 2008”
Brent Ozar
SQL Server Table Partitioning: Resources
Books Online

24. Questions?

25. Thank You Sponsors!
Visit the Sponsor tables to enter their end of day raffles.
Turn in your completed Event Evaluation form at the end of the day in the Registration area to be entered in additional drawings.
Want more free training? Check out the Houston Area SQL Server User Group which meets on the 2nd Tuesday of each month. Details at
5/14/2016