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The Schema Design talk given at the TriMug meetup in Durham, NC
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Schema DesignJ. Randall Hunt Developer and Evangelist at MongoDB
Who am I?
• J. Randall Hunt
• @jrhunt
• github.com/ranman
Why are you here?
• To learn about MongoDB
• To engage in the MongoDB community
• To get free stuff
Levels of Abstraction!
ORMs To Save The Day!
Why change something that's been around for 40
years?
10TB
Data Human Kind Has Produced Until 1991
Data Mankind Produces Every Day Since 2001
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NOSQL/NOREL
Relational Schema Design Focus on data storage
Document Schema Design Focus on data use
Why MongoDB?• Focus on commodity hardware, not insane machines
• Document Store
• Dynamic Schema
• Sensible Defaults
• Modern Scaling Infrastructure
How People Use MongoDB• Analytics
• Risk Management
• Caching Layer
• Recommendation Engines
• GIS
Nitty Gritty
RDBMS MongoDB Database � Database Table � Collection Row � Document Index � Index Join � Embedded Document Foreign Key � Reference
Documents?
{ "hello": "world" }
{ "_id": ObjectId("51638f8332e9bc556fe86de7"), "dstats": [ { "+": "5", "-": "0", "f": "gitstreamer.py" }, { "+": "3", "-": "3", "f": "post-commit.py" } ], "author": "ranman", "ts": ISODate("2013-04-08T19:48:11-0400"), "project": "gitstreamer", "msg": "turning this into a webapp" } !
CRUD
test> db.test.find() Fetched 0 record(s) in 1ms -- Index[none]
test> db.test.find() Fetched 0 record(s) in 1ms -- Index[none]test> db.test.insert({'hello': 'world'}) Inserted 1 record(s) in 1ms Insert WriteResult({ "ok": 1, "n": 1 })
test> db.test.find() Fetched 0 record(s) in 1ms -- Index[none]test> db.test.insert({'hello': 'world'}) Inserted 1 record(s) in 1ms Insert WriteResult({ "ok": 1, "n": 1 }) test> db.test.find({'hello': 'world'}) { "_id": ObjectId("52d61af21486ef9e06d6d41a"), "hello": "world" } Fetched 1 record(s) in 0ms -- Index[none]
test> db.test.update({'hello': 'world'}, {$set: {'hello': 'welt'}}) Updated 1 existing record(s) in 0ms Update WriteResult({ "ok": 1, "n": 1 })
test> db.test.find() Fetched 0 record(s) in 1ms -- Index[none]test> db.test.insert({'hello': 'world'}) Inserted 1 record(s) in 1ms Insert WriteResult({ "ok": 1, "n": 1 }) test> db.test.find({'hello': 'world'}) { "_id": ObjectId("52d61af21486ef9e06d6d41a"), "hello": "world" } Fetched 1 record(s) in 0ms -- Index[none]
Lots of Operators!
Enough already I know what MongoDB is! Teach me
schema design!
Library Management
• Patrons
• Books
• Authors
• Publishers
One To One Relations
patron = { _id: ObjectId("52d7173817d8bbd9564613cd"), name: 'Joe Schmoe' } !
address = { patron_id: ObjectId("52d7173817d8bbd9564613cd"), street: "100 Five Bridge Rd", city: "Clinton", state: "NC", zip: 28723 } >patron = db.patron.find({'name': 'Joe Schmoe'})[0] >db.address.find('patron_id': patron._id)
patron = { _id: ObjectId("52d7173817d8bbd9564613cd"), name: 'Joe Schmoe', address: { street: "100 Five Bridge Rd", city: "Clinton", state: "NC", zip: 28723 } } >db.patrons.findOne({'name': /Joe Schmoe/})
One To Many Relations
book = { _id: ObjectID(...), title: "MongoDB", authors: ['Kristina Chodorow', 'Mike Dirolf'], published_date: ISODate('2010-09-24'), pages: 216, language: 'English', publisher: { name: "O'Reilly Media", founded: "1980", location: "CA" } }
4 ways of modeling one-to-many (there are more)
• Embed the publisher
• Use publisher as the "foreign key"
• Use book as the "foreign key"
• Hybrid
publisher = { _id: "oreilly", name: "O'Reilly Media", founded: "1980", location: "CA" } book = { _id: ObjectID(...), title: "MongoDB", authors: ['Kristina Chodorow', 'Mike Dirolf'], published_date: ISODate('2010-09-24'), pages: 216, language: 'English', publisher_id: 'oreilly' }
publisher = { name: "OReilly Media", founded: "1980", location: "CA" books: [ ObjectId(...), ... ] } book = { _id: ObjectID(...), title: "MongoDB", authors: ['Kristina Chodorow', 'Mike Dirolf'], published_date: ISODate('2010-09-24'), pages: 216, language: "English" }
Hybrid Models
• We store the foreign key
• and the info relevant to the relation
patron = { _id: ObjectId("52d7173817d8bbd9564613cd"), name: "Joe Bookreader", address: {...}, join_date: ISODate("2011-10-15"), books: [ {_id: ObjectID(...), title: "MongoDB", author: "Kristina C.", ...}, {_id: ObjectId(...), title: "Postgres", author: "Randall H.", ...} ] }
Where do you put the foreign key• Array of books inside of publisher
• Makes sense when many means a handful of items
• Useful when items have bounds on potential growth
• Reference to a single publisher on each book
• Useful when items have unbounded growth
Other Things To Model
• Trees
• Queues
• Many-To-Many relationships
Thanks! @jrhunt