A short presentation (25') focused on why I think couchdb is cool, what he does really well and for what problems he should be used to solve

1. Webtechcon Milano 10/11/2010

2. gabriele lana
gabriele.lana@cleancode.it
twitter: @gabrielelana

3. “i can’t tell you
how i work in
25’ but i can
tell you why i
am cool”

4. what i am #1
document
oriented
database

5. key -> document
name: “Gabriele”
1 job: “Programmer”
born: “02/07/1977”
company: “CleanCode”
name: “Paolo”
2 job: “Manager”
born: “17/12/1965”
company: “BadCode”
name: “Enzo”
3 job: “Plumber”
born: “22/04/1982”
company: “CleanPipe”

6. complex values
name: “Gabriele”
1 job: “Programmer”
born: [ 2, 7, 1977 ]
company: “CleanCode”

7. map as filter
function(document) {
if (document.job === "Programmer") {
emit(document.id, document)
}
}
1 ... 1 ...
2 ... 2 ...
3 ... 3 ...

8. map as filter
function(document) {
if (document.job === "Programmer") {
emit(document.id, document)
}
}
yep is javascript

9. map -> index
function(document) {
emit(document.born, document)
}
19970702 ...
19651217 ... 19820422 ...

10. range queries are fast
function(document) {
emit(document.born, document)
}
19970702 ...
19651217 ... 19820422 ...

11. map -> reduce -> index
from: “Gabriele”
1 to: “Chiara”
at: [2010,11,11,21,30]
message: “...”
How many messages
sended from gabriele?

12. map -> reduce -> index
function(document) { function(from, messages) {
emit(document.from, 1) sum(messages)
} }
“Gabriele” 10
“Chiara” 127 “Renato” 45

13. index with complex key
function(document) {
emit([ document.from ].concat(document.at)), 1)
}
[ “Gabriele”,2010,11,11,21,30 ] 1

14. reduce by group levels
[ “Gabriele”,2010,11,11,21,30 ] 1
level 3 [ “Gabriele”,2010,11 ] 4
level 2 [ “Gabriele”,2010 ] 7
level 1 [ “Gabriele” ] 10

15. logarithmic update
map/
reduce

16. logarithmic update
map/
reduce

17. logarithmic update
(real time queries)
map/
reduce

18. crash only policy
append
only
multiversion
rev/0 rev/1
concurrency
control

19. replication
• master -> slave

20. replication
• master -> slave
• master -> slaves

21. replication
• master -> slave
• master -> slaves
• master -> master

22. replication
• master -> slave
• master -> slaves
• master -> master
• PEEr -> peer

23. sharding

24. usage patterns
oltp olap
Relatively Often complex
standardized and queries involving
simple queries aggregations.
Returning Periodic batch
relatively few jobs refresh the
records data

25. what i am #2
web
server

26. web server
http
• crud on documents
• documents attachments
• long polling changes
• proper caching
• lots of libraries
• firewall friendly

27. what i am #3
application
server

28. application server

29. application server

30. application server
• show document
• list documents
• authentication
• url rewrite
• good for small applications
• good for back offices

31. i have good friends

32. books...

33. questions?

34. gabriele lana
gabriele.lana@cleancode.it
twitter: @gabrielelana