This document provides an overview of CouchDB, a NoSQL database that uses JSON documents with a flexible schema. It demonstrates CouchDB's features like replication, MapReduce, and filtering. The presentation then shows how to build a mobile running app called Couch25K that tracks locations using CouchDB and syncs data between phones and a server. Code examples are provided in Objective-C, Java, and JavaScript for creating databases, saving documents, querying, and syncing.

1. 44
Peter Friese / Stefan Reichert, Zühlke Engineering
CouchDB mobile
From Couch To 5k in 1 Hour

2. Peter Friese
@peterfriese
peter.friese@zuehlke.com
xing.to/peter
http://peterfriese.de

3. Stefan Reichert
@stefanreichert
stefan.reichert@zuehlke.com
xing.to/stefanreichert
http://blog.wickedshell.net/

4. What we will cover today
1 What is CouchDB?
2 Serious amount of demos!
3 Couch25K - A Runner’s App

5. What is CouchDB?
1

6. CouchDB is...
CouchDB is...
A NoSQL Database.

7. CouchDB is...
Document-Oriented.
{
! "name": "Peter",
! "company": "Zühlke Engineering",
! "email": "peter.friese@zuehlke.com",
! "languages": [
! ! "Objective-C",
! ! "Java",
! ! "C#",
! ! "JavaScript"
! ]
}

8. CouchDB is...
Schema-Free.
Put anything
you like into
your CouchDB.
Really.

9. CouchDB is...
Erlang-Powered.

10. CouchDB is...
RESTful.
GET
PUT Fully embraces
POST HTTP verbs
DELETE

11. CouchDB uses...
http://research.google.com/archive/mapreduce.html
Map/Reduce (JavaScript).

12. CouchDB uses...
Map/Reduce (JavaScript).
Input
{"ip": "212.23.45.12","traffic": “18278", date: “2012-03-11”},
{"ip": "74.12.345.1","traffic": “345", date: “2012-03-11”},
{"ip": "212.23.45.12","traffic": “112244", date: “2012-03-12”},
{"ip": "212.23.45.12","traffic": “8657", date: “2012-03-13”},
{"ip": "74.12.345.12","traffic": “12", date: “2012-03-12”},
{"ip": "10.122.111.22","traffic": “122222", date: “2012-03-11”}

13. CouchDB uses...
Map/Reduce (JavaScript).
Mapper Input for Reducer
212.23.45.12 18278 212.23.45.12 18278
74.12.345.1 345 212.23.45.12 112244
212.23.45.12 112244 212.23.45.12 8657
212.23.45.12 8657
74.12.345.1 12 74.12.345.1 12
10.122.111.22 122222 74.12.345.1 345
10.122.111.22 122222

14. CouchDB uses...
Map/Reduce (JavaScript).
Input for Reducer After Reduce
212.23.45.12 18278 212.23.45.12 139179
212.23.45.12 112244
212.23.45.12 8657
74.12.345.1 12 74.12.345.1 357
74.12.345.1 345
10.122.111.22 122222 10.122.111.22 122222

15. CouchDB features...
Robust Replication.

16. CouchDB features...
Robust Replication.
Laptop
Phone
Server

17. Demos
2

18. Calling Home
curl localhost:5984
{"couchdb":"Welcome","version":"1.1.0"}

19. Creating a New DB
curl -X PUT localhost:5984/helloworld
{"ok":true}

20. Deleting a Database
curl -X DELETE http://
localhost:5984/helloworld
{"ok":true}

21. Creating a New Document
curl
-X POST
-H "Content-Type: application/json"
localhost:5984/helloworld
-d @peter.json
{"ok":true,"id":"f8e42aaa4bc77124c28
6be13f000054e","rev":"1-4dc37117e0da
26d9c50dc92d4cbb04cc"}

22. Curious? GET Your Document!
curl http://localhost:5984/helloworld/
f8e42aaa4bc77124c286be13f000054e
{
"_id": "f8e42aaa4bc77124c286be13f000054e",
"_rev": "1-4dc37117e0da26d9c50dc92d4cbb04cc",
"name": "Peter",
"company": "Zühlke Engineering",
"email": "peter.friese@zuehlke.com"
}

23. Anatomy of a Document
{
"_id": "f8e42aaa4bc77124c286be13f000054e",
"_rev": "1-4dc37117e0da26d9c50dc92d4cbb04cc",
"name": "Peter",
"company": "Zühlke Engineering",
"email": "peter.friese@zuehlke.com"
}
UUID - very
unique identifier

24. Anatomy of a Document
{
"_id": "f8e42aaa4bc77124c286be13f000054e",
"_rev": "1-4dc37117e0da26d9c50dc92d4cbb04cc",
"name": "Peter",
"company": "Zühlke Engineering",
"email": "peter.friese@zuehlke.com"
}
revision revision hash (body,
number counter attachment,
_deleted flag)

25. Welcome to Futon!
Admin interface for CouchDB
CRUD for Documents
Manage Views
Manage Replication

26. Couch25K - A Runner’s App
3

27. Basic Idea
2-way 2-way
Phone IrisCouch Phone

28. CouchDB Mobile
n e ?
P h o
o u r
n y
o

29. CouchDB Mobile
Your app CouchCocoa lib Ektorp lib Your app
CouchDB CouchDB

30. CouchDB Mobile
Your app CouchCocoa lib Ektorp lib Your app
TouchDB lib TouchDB lib
SQlite SQlite

31. CouchDB Mobile
“TouchDB is a lightweight CouchDB-
compatible database engine suitable
for embedding into mobile or desktop
apps. Think of it this way: If
CouchDB is MySQL, then TouchDB
is SQLite.” - Jens Alfke, Couchbase
Labs

32. Start a Local Couch
CouchTouchDBServer *server =
[CouchTouchDBServer sharedInstance];
NSAssert(!server.error,
@"Error initializing TouchDB server: %@",
server.error);
self.database = [server
databaseNamed:@"couch25k"];
NSError *error;
if (! [self.database ensureCreated:&error]) {
// raise error
self.connected = false;
}

33. Start a Local Couch
try {
TDServer touchDBServer = new TDServer(filesDir);
!
HttpClient httpClient = new
TouchDBHttpClient(touchDBServer);
CouchDbInstance couchDBInstance =
new StdCouchDbInstance(httpClient);
!
CouchDbConnector couchDBConnector =
couchDBInstance.createConnector(COUCH25K_DB,true);
! ...
} catch (IOException e) {
! Log.e(TAG, "Error starting TDServer", e);
}

34. Trackpoints
{
"run": "run-peterfriese-19",
"user": "peterfriese",
"lon": "9.990512659959458",
"time": "2012-03-24 07:39:27 +0000",
"lat": "53.73176022303823"
}

35. Saving a Trackpoint
NSDictionary *trackpointProperties =
[NSDictionary dictionaryWithObjectsAndKeys: (...)
CouchDocument *trackpointDocument =
[database untitledDocument];
RESTOperation* op = [trackpointDocument
putProperties:trackpointProperties];
[op onCompletion: ^{
if (op.error)
NSLog(@"Couldn't save the new item");
}];
[op start];

36. Saving a Trackpoint
Ektorp: JPA for CouchDB
public class TrackPoint extends CouchDbDocument
Repository Support
public class TrackPointRepository extends
! CouchDbRepositorySupport<TrackPoint>
... so saving a TrackPoint is pretty easy
trackPointRepository.add(trackPoint);

37. Sync with the Server
NSURL *url = [NSURL
URLWithString:
@"http://peterfriese.iriscouch.com/couch25k"];
[self.database replicateWithURL:url exclusively: YES];

38. Sync with the Server
Pull from Server
ReplicationCommand commandPull = new
ReplicationCommand.Builder()
.source(COUCH25K_REMOTE_DB)
.target(COUCH25K_DB)
.continuous(true).build();
try {
couchDBInstance.replicate(commandPull);
} catch (Exception exception) {
Log.e(TAG, exception.getMessage(), exception);
}

39. Sync with the Server
Push to Server
ReplicationCommand commandPush = new
ReplicationCommand.Builder()
.source(COUCH25K_DB)
.target(COUCH25K_REMOTE_DB)
.continuous(true).build();
try {
couchDBInstance.replicate(commandPush);
} catch (Exception exception) {
Log.e(TAG, exception.getMessage(), exception);
}

40. Demo

41. Display List of Runs (JavaScript)
Map Reduce
function(keys, values)
function(doc) {
{
emit(doc.run, 1);
return sum(values);
}
}
run-1 1
run-1 1
run-1 3
run-1 1
run-2 2
run-2 1
run-2 1

42. Display List of Runs (Obj-C)
Map
[design defineViewNamed: @"runs" mapBlock: MAPBLOCK({
id run = [doc objectForKey:@"run"];
if (run) emit(run, nil);
})
Reduce
reduceBlock:REDUCEBLOCK({
return [NSNumber numberWithInt:values.count];
})

43. Display List of Runs (Java)
Map
new TDViewMapBlock() {
public void map(Map<String, Object> doc,
TDViewMapEmitBlock emitter) {
if (doc.containsKey("run")) {
emitter.emit(doc.get("run"), doc.get("_id"));
}
}
}

44. Display List of Runs (Java)
(Re-) reduce
new TDViewReduceBlock() {
public Object reduce(List<Object> keys, List<Object>
values, boolean rereduce) {
if (rereduce) {
int sum = 0;
for (Object object : values) {
sum += (Integer) object;
}
return sum;
}
return values.size();
}
};

45. Filtering
Peter Stefan
Filter by name
sync 2-way sync 2-way
Phone IrisCouch Phone 2

46. Filtering
CouchDB
by_user:
function(doc, rq) {
if(doc.user == rq.query.username) {
return true;
}
return false;
}

47. Filtering
NSArray *replications =
[self.database replicateWithURL:url exclusively: YES];
CouchPersistentReplication *from =
[replications objectAtIndex:0];
from.continuous = YES;
from.filter = @"couch25k/by_user";
NSDictionary *filterParams = [NSDictionary
dictionaryWithObjectsAndKeys:
@"peterfriese", @"username", nil];
from.query_params = filterParams;

48. Filtering
Map<String, Object> queryParams =
new HashMap<String, Object>();
queryParams.put("username", "stefanreichert");
ReplicationCommand commandPull = new
ReplicationCommand.Builder()
.source(COUCH25K_REMOTE_DB)
.target(COUCH25K_DB).continuous(true)
.filter("by_user")
.queryParams(queryParams).build();
try {
! couchDBInstance.replicate(commandPull);
} catch (Exception e) {
! Log.e(TAG, exception.getMessage(), e);
}

49. Maps, please!

50. Query Trackpoints by Run
Map
mapBlock: MAPBLOCK({
NSString *run = (NSString *)[doc objectForKey:@"run"];
id time = [doc objectForKey:@"time"];
NSMutableArray *key = [[NSMutableArray alloc] init];
[key addObject:run];
[key addObject:time];
emit(key, doc);})
[run-peter-1, 2012-03-23 10:10] {lat:..., lon:...}
[run-peter-1, 2012-03-23 10:11] {lat:..., lon:...}
[run-peter-2, 2012-03-26 20:05] {lat:..., lon:...}
[run-peter-2, 2012-03-26 20:06] {lat:..., lon:...}
[run-peter-2, 2012-03-26 10:07] {lat:..., lon:...}

51. Query Trackpoints by Run
Query
CouchQuery *query = [[self.database
designDocumentWithName: @"couch25k"]
queryViewNamed: @"waypoints_by_run"];
CouchLiveQuery *livequery = [query asLiveQuery];
[livequery setStartKey:
[NSArray arrayWithObjects:self.runKey, nil]];
[query setEndKey:
[NSArray arrayWithObjects:self.runKey, @"ZZZ", nil]];

52. Query Trackpoints by Run
Map
new TDViewMapBlock() {
public void map(Map<String, Object> document,
TDViewMapEmitBlock emitter) {
if (document.containsKey("run")) {
document.get("run"), document.get("_id"));
}
}

53. Query Trackpoints by Run
Query
ViewQuery viewQuery = new
ViewQuery().designDocId("_design/TrackPoint")
.viewName("trackpoint_by_run")
.key(runId);
ViewResult result = db.queryView(viewQuery);
List<TrackPoint> trackPoints = new
ArrayList<TrackPoint>();
for (Row row : result.getRows()) {
TrackPoint trackPoint = get(row.getValue());
trackPoints.add(trackPoint);
}
return trackPoints;

54. And finally...
http://josephta.me/about-joseph-tame/

55. ... a Tribute to Steve Jobs
GPX
of J cou
rtes
ose y
ph
- T Tam
han e
ks!
http://bit.ly/HbDRod

56. Relax!
44

57. Thanks!
Peter Friese
Principal Consultant
rt @peterfr
Zühlke Engineering GmbH @stef anreiche iese
Am Sandtorkai 66
20457 Hamburg Availa
ble fo
+49 151 108 604 72 discu r con
ssing sultin
all th g,
rt
Reiche Engineer mobil ings
Stefan
Software
e and
Senior H frost
nginee
rin g Gmb y beve
E
Zühlke torkai 66 rages
nd
Am Sa rg
Hambu
20457
6
961 43 3
+ 49 173
PS: we’re hiring...