CouchConf-NYC-Best-practices-good-document-design

Best Prac*ces for Good Document DesignDus*n Sallings @dlsspy

QUICK POLL Normaliza)on

SCHEMA‐FREE DATABASE• schema deﬁni)on is op#onal at write )me –  no need to deﬁne schema before adding data – write any sort of JSON you’d like• schemas can be enforced• but (by default) only maBer when wri)ng queries 3

HOWEVER!There are constraints. 4

INHERENT SCHEMA sort of 5

UNIQUENESS• Document ID is the only (DB‐side) way to make  something unique• App could de‐duplicate from map/reduce –  but that can be tricky• So, be prepared to handle conﬂic)ng IDs 6

IMPLICIT BASICS 7

JSON DOCUMENTS{ “json”: “key / value pairs”, “_id”: “speciﬁed id or auto generated UUID”, “_rev”: “mvcc”, “keys are strings” : [1, 2, 3, “four”, null], “schema free” : true} 8

KEY NAMES• JSON Object restric)ons –  they’re all strings•  Couchbase Server reserves these preﬁxes on top‐ level keys –  “_” underscore ‐ also reserved by CouchDB –  “$” dollar signs• cannot have duplicate key names on a single level –  {“key”: 1, “key”: 2} is invalid (thankfully) 9

VALUES• JSON restric)ons –  objects, arrays, strings, numbers• Consider how you’ll be using it in your app –  template system constraints –  Mustache needs arrays of objects vs. arrays of arrays• Be careful of numbers as strings• Date formats –  ISO8601 –  unix )mestamps – output as an array for grouping reduc)ons 10

ONE DOC OR MULTIPLE DOCS? 11

DECISION MAKERS• what does this document look like in real life?• how oeen will I update this?• does this need its own revision/transac)on path? –  does all this data need upda)ng together? –  or rolled back together? 12

QUERYINGcan I get at the doc’s data easily? 13

UPDATING• When things change, do I want to update the doc? –  or record the document’s changes as individual docs• Frequently wriBen docs might make replica)on  harder due to higher conﬂict probability• Will I have de‐normalized por)ons of data on hand in  the client app when upda)ng? 14

REPLICATION the biggie! 15

REPLICATION• Where possible... –  avoid conﬂicts –  leverage small pieces• Keep uniqueness and conﬂicts in balance 16

CONVENTIONSpaving the caBle trails 17

CONVENTIONS & GOOD HABITS• “type”: “contact”• “created_at”: Unix )mestamp• “status”: some status for this doc (ex: published)• “tags”: [“couch”, “db”, “nosql”] 18

MORE CONVENTIONS• “created_by”: username –  typically from _users database• “proﬁle”: CouchApp proﬁle contents –  from _users database –  stored on the doc for convenience 19

TOOLS 20

VALIDATE_DOC_UPDATE• op&onal schema enforcement• func)on(newDoc, storedDoc, userCtx)• throw errors to prevent save• cannot modify newDoc• can enforce ﬁeld types, values, formats• can prevent docs or ﬁelds from being changed  (created_at, user)• runs every )me a document is updated –  even during replica)on 21

SAMPLE DOCS (IN  2.0) HANDY FOR QUICK DOC “SCHEMA” REFERENCING 22

ADVANCED DOCUMENT DESIGN more tools and tricks in this session 23

EXAMPLES 24

1.{2. "_id": "2011-10-20T00:32:58_101D8A2A000000F7",3. "_rev": "1-0c9914a4695b67a4f38cb5f8e345d28f",4. "reading": 22.98,5. "sn": "101D8A2A000000F7",6. "ts": "2011-10-20T00:32:58",7. "type": "reading"8.} 25

1. {2. "_id": "0017dcf0149c130229f35b537df48073",3. "_rev": "7-ef6c5723edafb9828dbc36467493341d",4. "old_id": 7343,5. "height": 1800,6. "keywords": [7. "wrx"8. ],9. "cat": "Public",10. "size": 1711223,11. "tnwidth": 194,12. "exif": {13. "EXIF ApertureValue": "367/100",14. /* ... */15. "EXIF SensingMethod": "One-chip color area",16. "MakerNote AEWarning": "Off",17. "Thumbnail Orientation": "Horizontal (normal)"18. },19. "descr": "My car had fun this weekend. It got all dirty in the snow and then ran into a sign. ",20. "ts": "2006-02-22T17:47:16",21. "addedby": "dustin",22. "width": 2400,23. "extension": "jpg",24. "tnheight": 146,25. "taken": "2006-02-21",26. "type": "photo",27. "annotations": [28. ],29. "_attachments": {30. "800x600.jpg": {31. "content_type": "image/jpeg",32. "revpos": 4,33. "digest": "md5-HB0NfWVLWeQJn8j79214Fw==",34. "length": 84388,35. "stub": true36. }, 37. // [...] 26

ANY QUESTIONS?• catch me in the lounge• or online: • @dlsspy • dsal on irc.freenode.net: #couchdb, #couchbase, #membase • dus)n@couchbase.com 27

CouchConf-NYC-Best-practices-good-document-design

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