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Become the nhibernate Guru

Become the nhibernate Guru. Torkel Ödegaard. torkel.odegaard@gmail.com. www.codinginstinct.com. Nhibernate?. ORM (Object-Relational Mapper). Transparent persistance. Persistence ignorance. Become the Guru. Identity map (L1 Cache) Unit Of Work (Session Flush) Cascading

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Become the nhibernate Guru

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  1. Become the nhibernate Guru

  2. Torkel Ödegaard torkel.odegaard@gmail.com www.codinginstinct.com

  3. Nhibernate? ORM (Object-Relational Mapper) Transparent persistance Persistence ignorance

  4. Become the Guru • Identity map (L1 Cache) • Unit Of Work (Session Flush) • Cascading • Attached / Detached • Proxy / Lazy loading • ID generation / unsaved-value • Concurrency • Legacy databases • Performance

  5. IStarShip

  6. Those WERE the droids I was looking for...

  7. MAPPing

  8. Mapping

  9. example

  10. session

  11. Session

  12. unit of work session.Flush()

  13. Flush Mode • Auto • Commit • Never • Unspecified

  14. Transaction Unit Of Work

  15. identity map An identity map is a database access design pattern  used to improve performance by providing a context-specific in-memory cache to prevent duplicate retrieval of the same object data from the database.

  16. identity map True

  17. identity map True

  18. identity map - Problems Same instance Will return instance from identity map

  19. identity map - Problems NHibernate.NonUniqueObjectException A different object with the same identifier value was already associated with the session Two instances with same id

  20. identity map - Problems NHibernate.HibernateException Identifier of an instance of TieFighter was altered …

  21. Cascading

  22. cascading • None • Save-update • Delete • Delete-orphan • All • All-delete-orphan

  23. Cascade & Save-update Transient (unsaved) instance Transient (unsaved) instance INSERT INTO Pilot .... INSERT INTO TieFighter ...

  24. Cascade & delete DELETE TieFighter ... DELETE Pilot ...

  25. Cascade & none Transient (unsaved) instance Transient (unsaved) instance NHibernate.TransientObjectException Object references an unsaved transient instance -save the transient instance before flushing

  26. Cascade & none

  27. Cascade & none

  28. Cascade & none UPDATE Pilot ....

  29. PRoxy

  30. PRoxy

  31. PRoxy

  32. Fetch Select / Lazy /N plus 1

  33. Fetch join

  34. inverse false

  35. concurrency

  36. Concurrency

  37. Concurrency - version

  38. Concurrency - version

  39. Concurrency - timestamp

  40. legacy • Composite primary keys • Relations on non-primary keys • Join • SQL Queries • DB Generated fields

  41. Property-ref

  42. Sql queries

  43. generated - insert

  44. performance • Batching • Eager loading (eliminate N+1) • Query Cache • L2 Cache

  45. Batching

  46. Batching

  47. i could go on an on... • NHibernate = endless number of features 

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