Modifying the schema of a production database is hard. If something goes wrong, the impact on both customers and the team can be enormous. And it can be hard or even impossible to rollback a database schema change if things go wrong. And the same is true for any architectural change for a production application. The Branch by Abstraction and Strangler Pattern makes significant application changes easier. Are there any similar patterns we can use to make production database changes less risky? Indeed, there are. The Expand/Collapse pattern is a blueprint for making the database migration. It makes the remodelling both reversible and safe. By expanding the application to accommodate both the old and the new schemas in parallel, we can give ourselves time to: Migrate any downstream dependencies on the old database schema Gain confidence that the migration is safe We contract the application to the new version, once we’ve satisfied that the old schema is no longer needed. The pattern helps to make significant, but necessary refactorings to your data model in a continuous delivery way. Most importantly, without threatening the robustness of your production applications. While working with our product, I’ve successfully applied this pattern to make major changes to the core of the application, all while serving customers in production. I’ve learned some important lessons about how to best implement the Expand/Contract pattern. In this session, I’ll share my experiences on how to avoid pitfalls and succeed at these kinds of major data remodelling with hardly any downtime. More details: https://confengine.com/agile-india-2019/proposal/8174/expand-contract-pattern-for-continuous-delivery-of-databases Conference link: https://2019.agileindia.org

1. Expand Contract
Pattern
Continuous Delivery for Databases
@leenasn

2. https://pixabay.com/en/hands-hand-raised-hands-raised-220163/

3. Yogatree
Digital Marketing for Yoga Centres
getyogatree.com

4. Evolvability https://pixabay.com/en/juggle-artists-circus-money-1027844/

5. Database? https://pixabay.com/

6. https://unsplash.com/photos/elayN_YscVg
Slow

7. High risk https://pixabay.com/en/balance-risk-courage-risky-3062272/

8. Less risky? https://pixabay.com/

9. A database refactoring is a small change to
your database schema (the table structures,
data itself, stored procedures, and triggers)
which improves its design without changing its
semantics.
http://databaserefactoring.com/

10. ● Enables Continuous Delivery
● Supports evolutionary development
http://databaserefactoring.com/

11. https://www.dreamstime.com/stock-photos-example-stamp-image28420393

12. Split table

13. Transition

14. New Schema

15. Refactoring Process

16. Split Column
customer
booking_date
status
trial_bookings

17. Transition

18. New Schema

19. Refactoring Process

20. https://martinfowler.com/articles/evodb.html
Expand Contract

21. https://www.dreamstime.com/abcs-color-colorful-wooden-blocks-image139644010Basics

22. Versioning https://git-scm.com/downloads/logos

23. http://demographicwinter.org/automation-gears-8231/
Automation

24. https://pixabay.com/en/strategy-arrows-building-startup-3224515/

25. Parallel Change - Patterns
https://pixabay.com/photos/sand-pattern-wave-background-white-2005066/

26. https://martinfowler.com/bliki/BranchByAbstraction.html
Branch by Abstraction

27. https://martinfowler.com/bliki/BranchByAbstraction.html
Branch by Abstraction

28. https://martinfowler.com/bliki/BranchByAbstraction.html
Branch by Abstraction

29. https://pixabay.com/en/magnifying-glass-facts-examine-1607160/

30. Software Releases Without Major Problems @ Facebook
https://www.forbes.com/sites/quora/2013/08/12/how-do-facebook-and-google-manage-software-releases-without-causing-major-problems/

31. Move fast and break nothing @ Github
https://zachholman.com/talk/move-fast-break-nothing/

33. Murphy’s Law https://www.flickr.com/photos/smemon/5471883005

34. Low risk releases https://pixabay.com/en/button-red-round-shiny-155149/

35. Small Batches https://unsplash.com/photos/6jpdeeA2GBU

36. Release frequently
https://www.slideshare.net/jallspaw/ops-metametrics-the-currency-you-pay-for-change

37. References

38. References
Large scale changes with Branch by Abstraction
Legacy Application Strangulation - Case studies
Split Table - Database Refactoring
Continuous Delivery of Databases
Expand Contract Pattern - Continuous Delivery of Databases
Database Refactoring
Four Principles of Low-Risk Software Releases
Branch by Abstraction
Move Fast @ Github

39. Leena S N
@leenasn / leena.sn@multunus.com
https://medium.com/@leenasn