CouchDB: a Database for the Web

Nesta apresentação irei falar sobre conceitos do banco de dados CouchDB (http://couchdb.apache.org/), como design documents, views, show e list functions. Também irei falar sobre replicação e change notifications, que são poderosas features deste banco de dados NoSQL.

Transcript

1. Sunday, September 30, 12
2. Sunday, September 30, 12
3. Summary • Introduction • MVCC • The Core API • Design Documents • Views, Show Functions, List Functions • Change Notifications • Be Careful... • References Sunday, September 30, 12
4. Introduction • Built on the Erlang Platform • NoSQL Database • Schemaless • MapReduce • B-tree storage engine - O(log N) • Eventual Consistency by incremental replication Sunday, September 30, 12
5. MVCC • Multi-Version Concurrency Control • No Locking • Documents are versioned • Each read operation is guaranteed a consistent view of the database Sunday, September 30, 12
6. The Core API • Server • Databases • Documents • Replication Sunday, September 30, 12
7. Server API curl http://127.0.0.1:5984/ {"couchdb":"Welcome","version":"0.10.1"} Sunday, September 30, 12
8. Databases API curl -X PUT http://127.0.0.1:5984/albums {"ok":true} Sunday, September 30, 12
9. Documents API curl -X PUT http://127.0.0.1:5984/albums/ 6e1295ed6c29495e54cc05947f18c8af -d '{"title":"There is Nothing Left to Lose","artist":"Foo Fighters"}’ {"ok":true,"id":"6e1295ed6c29495e54cc05947f18c8af ","rev":"1-2902191555"} Creating a Document Sunday, September 30, 12
10. Documents API curl -X GET http://127.0.0.1:5984/albums/ 6e1295ed6c29495e54cc05947f18c8af {"_id":"6e1295ed6c29495e54cc05947f18c8af","_rev": "1-2902191555","title":"There is Nothing Left to Lose","artist":"Foo Fighters"} Retrieving a Document Sunday, September 30, 12
11. Documents API curl -X PUT http://127.0.0.1:5984/albums/ 6e1295ed6c29495e54cc05947f18c8af -d '{"_rev":"1-2902191555","title":"There is Nothing Left to Lose", "artist":"Foo Fighters","year":"1997"} {"ok":true,"id":"6e1295ed6c29495e54cc05947f18c8af ","rev":"2-2739352689"} Updating a Document Sunday, September 30, 12
12. Replication curl -X PUT http://127.0.0.1:5984/albums-replica curl -vX POST http://127.0.0.1:5984/_replicate -d '{"source":"albums","target":"albums-replica"}' Sunday, September 30, 12
13. Design Documents • Special type of CouchDB document that contains application code • Views • Shows • Lists Sunday, September 30, 12
14. Views function(doc) { if(doc.date && doc.title) { emit(doc.date, doc.title); } } Map Function GET /database/_design/ designdocname/_view/viewname { "total_rows": 3, "offset": 0, "rows": [ { "key": "2009/01/15 15:52:20", "id": "hello-world", "value": "Hello World" }, { "key": "2009/02/17 21:13:39", "id": "bought-a-cat", "value": "Bought a Cat" }, { "key": "2009/01/30 18:04:11", "id": "biking", "value": "Biking" } ] } Response API Sunday, September 30, 12
15. Views Sunday, September 30, 12
16. Views function (key, values, rereduce) { return sum(values); } Reduce Function • Reduce: results emitted by map function • Rereduce: results returned by the reduce function itself function(null, [3, 1], true) { return sum([3, 1]); } Rereduce Function Sunday, September 30, 12
17. Show Functions { “_id” : “_design/mydesign”, “shows” : { “myshow” : “function(doc, req) { return '<h1>' + doc.title + '</h1>'; }” } } Show Function GET /mydb/_design/mydesign/_show/ myshow/72d43a93eb74b5f2 API • Query parameters • Etags • Functions and templates (CouchApp) Sunday, September 30, 12
18. List Functions { "_id" : "_design/foo", "_rev" : "1-67at7bg", "lists" : { "bar" : "function(head, req) { var row; while (row = getRow()) { ... send() ... } }", "zoom" : "function() { return 'zoom!' }", } } List Function GET /mydb/_design/mydesign/_list/ mylist/myview API Sunday, September 30, 12
19. Change Notifications { "results":[ {"seq":1,"id":"test","changes":[{"rev":"1- aaa8e2a031bca334f50b48b6682fb486"}]}, {"seq":2,"id":"test2","changes":[{"rev":"1- e18422e6a82d0f2157d74b5dcf457997"}]} ], "last_seq":2 } GET /mydb/_changes API • feed=longpoll • feed=continuous • filters Sunday, September 30, 12
20. Be careful... • It’s not a relational database!!! • Linked documents when include_docs • Views are updated on read access • Changing a view rebuild all views of the design document • “Stale” views • Pre-warm views • Database compaction and cleanup Sunday, September 30, 12
21. References • CouchDB (http://couchdb.apache.org/) • CouchApp (http://couchapp.org) • CouchDB The Definitive Guide (http:// guide.couchdb.org/) • Ruby: couchrest (https://github.com/ couchrest/couchrest), couchrest_model (https://github.com/couchrest/ couchrest_model) Sunday, September 30, 12