Title: Voyage by example Speaker: Esteban Lorenzano Thu, August 21, 11:00am – 11:30am Video Part1: https://www.youtube.com/watch?v=1szVgKQm474 Video Part2: https://www.youtube.com/watch?v=vxork8Kckh8 Description Voyage is a framework to abstract over NoSQL databases and provides nice object-oriented features to save objects. Bio: Esteban Lorenzano, 42 years. Programmer since ever, Full-time Smalltalker since 2007 and Pharo enthusiast since almost its every beginning, after owning his own company and spend some years teaching at different universities in Argentina, he currently works de development of Pharo itself, at the RMoD team of INRIA (France)

1. Voyage by example
tips and tricks on persisting object models

2. Esteban Lorenzano
Pharo core developer
INRIA - RMoD
http://smallworks.eu

3. Why?
• You already know about Voyage
• You already attended to a tutorial last year
• But there are some recurrent problems people find
when trying to use it
• And I’m still seeing a lot of people that could be
using it and they chose other solutions

4. What is Voyage? (1)
• Simple abstraction layer to map objects into a database
- Very well suited for document databases, but in theory,
the approach will work for other kind of repositories
‣ There was (long time ago) a Voyage-GLORP backend
‣ There was (even more time ago) a Voyage-
ImageSegment backend
- Voyage-Memory, Voyage-Mongo

5. What is Voyage? (2)
• Did I said is simple?
• it ensures object identity
• it provides error handling
• it implements a connection pool

6. Voyage principles
• Behavioural complete (for common usage), but
decoupled approach also possible.
• Same design for different backends, but not a
common abstraction
- There is no such thing as a “voyage query
language”, etc.
- is a bit more work for users who want to switch,
but a lot more happiness for the program itself

7. Voyage ultimate goal
To be the GLORP for NoSQL databases

8. The problem to solve

9. Impedance mistmatch
Class A Class B Class C
Table A Table B Table C
1..*
*..*
Ideal relational model

10. Impedance mistmatch
aColection
anObject otherObject
firstObject
secondObject
thirdObject
Real object model

11. Impedance mistmatch
aColection
anObject otherObject
Real object model
firstObject
secondObject
thirdObject

12. Impedance mistmatch
aColection
anObject otherObject
Real object model
firstObject
secondObject
thirdObject

13. So, what about those tips?

14. Think in objects

15. A simple model
*..*
Hero Power

16. Persist
(Hero named: ‘Groot’)
addPower: ((Power named: ‘Plant Control’)
level: #epic;
yourself);
save.

17. Persist
{
_id: OID(…),
#version: …,
#instanceOf: ‘Hero’,
name: ‘Groot’,
powers: [ { #collection: ‘Power’, __id: OID(…) } ]
}
!
{
_id: OID(…),
#version: …,
#instanceOf: ‘Power’,
name: ‘Plant Control’,
level: #epic,
heroes: [ #collection: ‘Hero’, __id: OID(…) ]
}

18. Take control

19. A simple model
(a bit more complete)
*..*
Hero Power
1..*
Equipment
Container Pistol
1..*

20. Persist
(Hero named: ‘Star-lord’)
addEquipment: (Container
addItem: Pistol new;
yourself);
save.

21. Persist (1)
{
_id: OID(…),
#version: …,
#instanceOf: ‘Hero’,
name: ‘Star-lord’,
powers: [],
equipment: [ {
#instanceOf: ‘Container’,
‘items’, [
{ #instanceOf: ‘Pistol’ } ] } ]
}

22. Persist (2)
{
_id: OID(1),
#version: …,
#instanceOf: ‘Hero’,
name: ‘Star-lord’,
powers: [],
equipment: [ { #collection: ‘Equipment’, __id: OID(2) } ]
}
!
{
_id: OID(2),
#version: …,
#instanceOf: ‘Container’,
items: [ { #collection: ‘Equipment’, __id: OID(3) } ]
}
!
{
_id: OID(3),
#version: …,
#instanceOf: ‘Pistol’,
}

23. Integrity is a
consequence

24. Allowing missing content
• We do not have foreign keys
- So we cannot do things like “ON DELETE
CASCADE”
- Even delete validations are difficult
‣ Imagine “hero” has a “power”,and I remove the
“power”. How can the hero notice it?

25. Persist
mongoContainer
<mongoContainer>
!
^ VOMongoContainer new
collectionName: ‘powers’;
enableMissingContent;
yourself

26. Querying smart

27. Query (1)
Hero
selectMany: [ :each | … ]
sortBy: { #name -> VOOrder ascending } asDictionary
limit: 100
offset: 100

28. Query (2)
Hero
selectMany: {
‘name’ -> {
‘$regexp’ -> ‘^G.*’.
‘$options’ -> ‘i’
} asDictionary
} asDictionary

29. Adapt schemes

30. The “scheme is not mine”
problem
• You can move meta-information to your program
• Magritte-Voyage gives you a lot of power
• You can extend/modify parts of the updating
system too (like versioning)

31. Meta-information
{
_id: OID(…),
#version: …,
#instanceOf: ‘Hero’,
name: ‘Star-lord’,
powers: [],
equipment: [ {
#instanceOf: ‘Container’,
‘items’, [
{ #instanceOf: ‘Pistol’ } ] } ]
}

32. Meta-information
{
_id: OID(…),
#version: …,
#instanceOf: ‘Hero’,
name: ‘Star-lord’,
powers: [],
equipment: [ {
#instanceOf: ‘Container’,
‘items’, [
{ #instanceOf: ‘Pistol’ } ] } ]
}

33. Meta-information
{
_id: OID(…),
name: ‘Star-lord’,
powers: [],
equipment: [ {
‘items’, [ {} ] } ]
}

34. Voyage 2.0
• Root detection (enhance save & update)
• Cyclic detection
- Add strategy to persist cycles even without roots (It has some
consequences (in querying, etc.), so it will be optional)
• integrity validations
- #removeWithDependencies
• Materialisation customisations
- #readRaw
• Add backend: Riak

35. Use it today!
Gofer it
smalltalkhubUser: ‘Pharo’ project: ’MetaRepoForPharo30’;
configurationOf: ‘VoyageMongo’;
loadStable.
Thanks!!
Esteban Lorenzano - 2014