DATAMAPPERcontagion

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Datamapper is not only an

ORM Object-Relational Mapping

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Mapping class Post include DataMapper::Resource property :id, Serial property :title, String property :body, Text property :created_at, DateTime

has n, :comments end

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Not that different?

DB adaptors

STI

Association Migration

Hooks

Validation

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Different!

Faster

Easier

Flexible

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Identity Map

@p = Post.first

@p.comments.each do |c|

c.post.object_id == @p.object_id

end

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Loaded Set>> @p = Post.all=> [#<Post id=1>, #<Post id=2>]

>> @p.class=> DataMapper::Collection

>> @p[0].colleaction=> [#<Post id=1>, #<Post id=2>]

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Strategy Eager Loading

@posts = Post.all@posts.each do |p| puts p.user.nameend

2 Queriesno more n+1 or :include

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Lazy Loading@posts = Post.all#select id,title,created_at from posts;

@posts.each do |p| puts p.body #select body from posts where ....;end

Only load what you need( :fetch in 1.0? )

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Lazyp = Post.all

# no query happened!

p[0]#select * from posts limit 1

Wait for the kicker methods: each, map, count, etc.

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Scopedreview = Post.all(:title.like =>‘review’ )

my_review = yes_p.all(:user_id =>my_id)

conditions are joined together when the kicker kicks in

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Query Path

Post.all('comments.email.like' => 'contagion%' )

# SELECT "posts"."id", "posts"."created_at" FROM "posts" INNER JOIN "comments" ON ("posts"."id" = "comments"."post_id") WHERE ("comments"."email" LIKE 'contagion%') ORDER BY "posts"."id"

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Go off the Golden Pathrepository(:default).adapter.resource_naming_convention = DataMapper::NamingConventions::Resource::Underscored

class Stock property :target_symbol, String, :key => trueproperty :target_type_id, String, :key => true

repository(:legacy) do property :target_name, Stringend

end

Custom Naming ConventionComposite Keys

Multiple databases

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Datamapper is not only an

ORM Object-Relational Mapping

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Data

DatabaseDatabaseDatabasesDatabaseDatabaseFiles

DatabaseDatabaseWeb Services

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Merb Rails Your App

DataMapper

DO

DB

Application

Adapters

Data Sources

Architecture

REST

Web

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• 50 lines of code (read only)

• 1 hour (because I am stupid..)

• unified interface

• works with association !!

My Stupid MemCache Adaptor

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Modular

• rubygems

• dataobject

• dm-core

• dm-more

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Custom Type

• Serial : Integer with auto increment

• CSV : Serialize array into string

• YAML、JSON

• Custom :

• implements load / dump / typecast

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Auto Validation

property :email, :nullable => false, :length => (1..255), :format => :email_address

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