MongoDB: ObjStorSol + Des+Map’n

Yeah, I shortened that… but not to OSSDnM

… AppServer - J2EE (JBoss, Resin) Hosted AppServices - Google AppEngine Datastore - Objectify (GAEJ ORM/ODM) MongoDB – Morphia (ODM)

Community Developer (and more)

How I got here…

Basic Expectations No transactions (but atomic updates) Memory mapped data files Document store Fast-N-Loose by default (no safe/w/GLE) Indexing order matters; query optimizer

helps One writer (serialized writes) One JS thread (M/R, $where, group) Many query threads (non-js) BSON everywhere

What is the shell?

•vars•function

s•data

structs + types

Embedded JavaScript Interpreter

•ObjectId("...")

•new Date()

•Object.bsonsize()

Global Functions and Objects

•db["collection"].find/count/update

•short-hand for collections

MongoDB driver Exposed

•Doesn't require quoted keys

•Don’t copy and paste too much

JSON-like stuff

What is it good for? Debugging Testing Administration Scripting Glue Not building apps, probably…

Shell Demo

Single Collection, Inheritance One – Many

◦ Embedded◦ Reference

On the one -> Array of refs On the Many -> Add a ref field

Trees Many – Many

◦ Prob. best to store on only one side.

Designs

{ _id : "scotthernandez", name : "Scott Hernandez", desc : "that guy", groups : [ "users", "admins", "fishermen" ]}

People - Groups

{ "_id" : "users", "desc" : "normal users“ },

{ "_id" : "fishermen", "desc" : "people who fish“ },

{ "_id" : "admins", "privledges" : 2, "desc" : "administrative users“ }

Group - People

blog =: { text: “I like to swim”, author: “scott”,comments: [

{author:”ralph”, text:”me2”, replies:[ {author:”liz”, text:”doesn’t every1?”}]},{author:”jeff”, text:”good to know”}

],ts:Date(…)

}

Tree

Raw MongoDB Driver◦ Map<String, Object> view of objects◦ Rough but dynamic

Morphia (type-safe mapper)◦ POJOs◦ Annotation based (similar to JPA)◦ Syntactic sugar and helpers

Others◦ Code generators, other jvm languages

Java Library Choices

BSON Package◦ Types◦ Encode/Decode◦ DBObject (Map<String, Object>)

Nested Maps Directly encoded to binary format (BSON)

MongoDB Package◦ Mongo◦ DBObject (BasicDBObject/Builder)◦ DB/DBColletion◦ DBQuery/DBCursor

MongoDB Java Driver

Data Types◦ int and long◦ Array/ArrayList◦ String◦ byte[] – binData◦ Double (IEEE 754 FP)◦ Date (ms since epoch UTC)◦ Null◦ Boolean◦ JavaScript String◦ Regex◦ ObjectId (ts(4)+ host(3) + pid(2)+ incr(3) ) 12-byte

BSON Package

Morphia: MongoDB Mapper Maps POJO Type-safe Access Patterns:

DAO/Datastore/RollYourOwn Data Types Low performance overhead JPA like

Many concepts came from Objectify (GAE)

Annotations @Entity(“collectionName”) @Id @Transient (not transient) @Indexed(…) @Property(“fieldAlias”) @AlsoLoad({aliases}) @Reference @Serialized [@Embedded]

Lifecycle Events @PrePersist @PreSave @PostPersist @PreLoad @PostLoad

EntityListeners EntityInterceptor

Datastore Basics get(class, id) find(class, […]) save(entity, […]) delete(query) getCount(query) update/First(query, upOps) findAndModify/Delete(query, upOps)

Basic POJO

@Entityclass Person {

@Id ObjectId name;

SexEnum sex;

@IndexedInteger height;

}

Queries

Datastore ds = …

Query q = ds.createQuery(Person.class);

q.field(“height”).greaterThan(155).limit(5);

for(Person p : q.fetch()) print(p);

Person me = q.field(“name”).startsWith(“sc”).get();

Save whole object graphs (get/save)

Update parts (embedded objects)◦ Un/set fields◦ Push/pop arrays (lists)◦ Increment numeric fields

◦ Any combination of the above

Get/Save or Update

Update Operations set(field, val) unset(field)

inc(field, [val]) dec(field)

add(field, val) addAdd(field, vals)

removeFirst/Last(field) removeAll(field, vals)

Update existing props Update w/new props

Examples

Update

Datastore ds = …Query q = ds.find(Person.class, “name”, “scott”);UpdateOperation uo =

ds.createUpdateOperations(cls)

uo.set(“city”, “seattle”).set(“lastUpdated”, new Date());

UpdateResults res = ds.update(q, uo);if(res.getUpdatedCount() > 0) //do something?

Morphia Relationships Annotations [@Embedded]

◦ Load/Save with Entity◦ Update

@Reference◦ Stored as DBRef(s)◦ Loaded with Entity◦ Not automatically saved

Key<T>◦ Stored as DBRef(s)◦ Just a link, but resolvable by Datastore/Query

Or… ScottHernandez@gmail.com

Questions?