CouchConf-Chicago-Best-Practices-Good-Document-design

Best Practices for Good Document DesignDustin Sallings @dlsspy

SCHEMA-FREE DATABASE• schema deﬁnition is optional at write time – no need to deﬁne schema before adding data – write any sort of JSON you’d like• schemas can be enforced• but (by default) only matter when writing queries 2

HOWEVER!There are constraints. 3

INHERENT SCHEMA sort of 4

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 conﬂicting IDs 5

IMPLICIT BASICS 6

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} 7

KEY NAMES• JSON Object restrictions – 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) 8

VALUES• JSON restrictions – 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 timestamps – output as an array for grouping reductions 9

ONE DOC OR MULTIPLE DOCS? 10

THIS IS NOT A DOCUMENT 11

THIS IS NOT A DOCUMENT 12

NOPE 13

DECISION MAKERS• what does this document look like in real life?• how often will I update this?• does this need its own revision/transaction path? – does all this data need updating together? – or rolled back together? 15

QUERYINGcan I get at the doc’s data easily? 16

UPDATING• When things change, do I want to update the doc? – or record the document’s changes as individual docs• Frequently written docs might make replication harder due to higher conﬂict probability• Will I have de-normalized portions of data on hand in the client app when updating? 17

REPLICATION the biggie! 18

REPLICATION• Where possible... – avoid conﬂicts – leverage small pieces• Keep uniqueness and conﬂicts in balance 19

CONVENTIONSpaving the cattle trails 20

CONVENTIONS & GOOD HABITS• “type”: “contact”• “created_at”: Unix timestamp• “status”: some status for this doc (ex: published)• “tags”: [“couch”, “db”, “nosql”] 21

MORE CONVENTIONS• “created_by”: username – typically from _users database• “proﬁle”: CouchApp proﬁle contents – from _users database – stored on the doc for convenience 22

TOOLS 23

VALIDATE_DOC_UPDATE• optional schema enforcement• function(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 time a document is updated – even during replication 24

SAMPLE DOCS (IN 2.0) HANDY FOR QUICK DOC “SCHEMA” REFERENCING 25

ADVANCED DOCUMENT DESIGNmore tools and tricks in this session 26

EXAMPLES 27

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.} 28

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. // [...] 29

Q&A Panel with Couchbase Experts Submit your questions for ourCouchbase Q&A at the end of the conference to:couchconfchicago@couchbase.co m

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