What do you need to keep in mind when using ORM, how it will affect your needs and what are the disadvantages of using and advantages of not using ORM.

1. Why not ORM? Michal Špaček, Skype; WebExpo 2010 , Prague

2. OMGWTF ORM ?

3. O bject- R elational M apping !

4. ORM, SRSLY ?

6. ORM… … maps relational databases to objects says František Tröster

7. ORM… … maps relational databases to objects says František Tröster … maps objects to relational databases says Jiří Knesl

8. ORM… … maps relational databases to objects says František Tröster … maps objects to relational databases says Jiří Knesl … is a technique for converting data between incompatible type systems in OOP languages says Wiki Pedia

9. ORM is like …

10. … TDD

11. Best thing since sliced bread . Or maybe not .

12. ORM is said to allow the database systems swap „ on the fly “…

14. … , but have anyone seen it, ever ?

15. Most of the times you'll end up changing bunch of other things too, so it's not that easy as it might seem .

16. When your O/R mapper goes bananas …

19. Using ORM and want to refactor relations ?

20. Do it, pretty please, but you have to refactor code too…

21. … and you need to deploy all the changed stuff at once !

23. Put your business logic into the database !

27. Database code can be tested separately from the rest of the code

28. Application code tests do not need a connection to the database

29. Forget explicit transactions ( BEGIN & COMMIT ) if you can has your codes wrapped in functions

30. You'll get …

32. Every query can be executed on different machine

36. Because we got no transactions

37. Teams of database developers and admins …

38. … can monitor functions and their performance

39. … can redirect functions to be executed in different database when something goes horribly wrong

40. … are generally useless while using ORM http://www.xkcd.com/303/ ORM, DUDE!

41. While without ORM …

43. Will YOU stop using ORM?

45. refactoring relations

46. multiple technologies

47. tricky testing

48. inefficient connection pooling

49. admins are hopeless, if any

50. performance monitoring and control