Time to Use the Columnstore Index
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Columnstore has been available since SQL Server 2012. However, when it was introduced, it just wasn't quite ready for most people to use. Times have certainly changed. Now, it's time to use the columnstore index.
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Time to Use the Columnstore Index
- 1. Time to Use the Columnstore Index GRANT FRITCHEY, PRODUCT ADVOCATE, REDGATE SOFTWARE
- 2. Goals Understand how the columnstore index works and how it’s different than traditional, row store, indexes Learn the limitations and gotchas around the columnstore index Study places where columnstore benefits performance
- 4. Row Store ID Name Description Date 1 Grant Doof 1/10/17 2 Jeff Not a doof 3/4/55 3 Gabby Smart 9/2/92 4 Jeff Not a doof 8/6/73 5 Achmed Smart 1/10/17 6 Jeff Not a doof 11/22/87 7 Suzanne Not a doof 1/10/17
- 5. Row Store Heap Clustered Index Memory-Optimized Table
- 7. Columnstore
- 8. Columnstore Index Use Prior to 2016 (sp1), Enterprise only Clustered columnstore (2014+) Nonclustered columnstore Columnstore on memory- optimized table (2016+) B-tree indexes on clustered columnstore (2016+) Filtered nonclustered columnstore (2016+) It all works with Azure SQL Database
- 9. Columnstore Limitations: Data Types NTEXT, TEXT, IMAGE VARCHAR/NVAR CHAR/VARBINAR Y(MAX), below 2017 ROWVERION/TI MESTAMP SQL_VARIANT (a feature, not a bug) CLR (including spatial & hierarchy) XML GUID, 2012 only
- 10. Columnstore Limitations: Nonclustered Max 1024 columns No sparse columns Cannot use ALER INDEX No INCLUDE Can’t ASC/DESC
- 11. Columnstore Limitations Persisted computed columns Non-persisted computed column in clustered columnstore, 2017+ Page or row compression Replication Filestream
- 12. Columnstore Limitations: 2014 or Less Change Tracking Change Data Capture Readable Secondary – clustered columnstore only Multple Active Result Sets (MARS) Views or Indexed Views
- 14. Loading Columnstore 102,400 rows – Recommended batch size 1,048,576 rows per rowgroup Don’t pre-sort data Trickle loads & modifications Deletes require reorg/rebuild Inserts added to delta group Updates are logical to delta group Parallel Data Loads
- 15. Additional Behavior Snapshot Isolation Support: 2016+ Columnstore on table creation: 2016+ Availability Group Support: 2012+ Partitioning: 2012+
- 16. Maintenance Reorganize 2016+ Rebuild Removes fragmentation Moves rows from delta store Physically deletes deleted rows Statistics, no
- 17. Why Is Columnstore Faster First, last, always, it depends on the type of query Data Compression Column Elimination Rowgroup Elimination Batch Mode Execution Aggregate Pushdown (2016+) String Predicate Pushdown (sketchy, but interesting)
- 18. Batch Mode Execution Columnstore Only 64 to 900 rows/batch Use the Execution Plan to understand Parallel execution required for 2012 & 2014
- 19. Recommended Columnstore Use First, determine data access path Second, understand the data load process Third, know your queries Fourth, generally, greater than 100k rows Better with 1 million + Mix and Match
- 20. When To Use Columnstore Index Fact Tables Large Dimension Tables Data Warehousing in general Analytical Queries Aggregate Queries Lots of Large Scans
- 21. Resources Niko Negebauer: http://www.nikoport.com/columnstore/ Simple Talk: https://www.red-gate.com/Search/?s=columnstore&t=simpletalk SQL Server Central Stairway: https://www.sqlservercentral.com/stairways/stairway-to- columnstore-indexes My Resources: ◦ Code: https://github.com/ScaryDBA/PresentationCode ◦ Slide: https:/slideshare
- 22. Goals Understand how the columnstore index works and how it’s different than traditional, row store, indexes Learn the limitations and gotchas around the columnstore index Study places where columnstore benefits performance