datamapperthe persistence framework

who am I?

(Booth 501)

DataMapper

datamapper

object relational mapper

like activerecord

like activerecord★ DB adapters★ migrations★ associations★ one-to-one★ one-to-many★ many-to-one

★ many-to-many★ -through★ polymorphic

★ lifecycle events★ sti★ etc.

drops into Rails1.0

(or merb)0.9

DataMapper

Merb Rails

DO.rb YAML IMAP

Application

Adapters

Data Stores

architecture

some caveats

1.0

work in progress0.9

be prepared for code

why did we build it?

identity map

Foo[1]

Foo[1]

Foo

id = 1

...

foo[1] == foo[1]#=> true

loadedset

LoadedSet

foo.all

Foo

id = 1

...

Foo

id = 2

...

Foo

id = 3

...

Foo

id = 4

...

Foo

id = 5

...

Foo

id = 6

...

composite keys

belongs_to :project, :child_key => [:name, :tag]

legacy data

naming conventions(yours)

naming conventionsunderscored

foo::barBaz => foo/bar_baz

naming conventionsunderscoredandpluralizedfoo::barBaz => foo_bar_bazs

naming conventionsunderscoredandpluralizedwithoutmodule

foo::barBaz => bazs

naming conventionsyaml

foo::Bar => foo/bars.yaml

support for multiple databases(even in the same model)

Post.all(:repository => :legacy)

Post.all # :repository => :default

prepared statements1.0

custom types

embedded values1.0

Employment

id<Integer>

person<Person>

start<Date>

end<Date>

salary<Money>

salary_cur: char

salary_amt: dec

end: date

start: date

person_id: int

id: int

Employments

declared propertiesproperty :id, :key => true

robust queries

Child.all( “mother.last_name.like” => “Jane%”, :name.like => “Jim”)

dirty tracking

modularity

unified interface for drivers

•connections

•commands

•readers

•cursors (forward-only)

•quoting

• transactions

Connection Pool

Connection Connection Connection Connection Connection

“select * from foos where id = ?”

Command

create_command

execute_reader Reader next values next ...

execute_reader(12) => select * from foos where id = 12

works today on:mysql, sqlite, postgres

fast, written in C

simple interface for adapters

•read by key

•read by query

•update by key

•update set

•delete

• (optional: transactions)

salesforce adapter in 200 LOC

Errors

Operators

NamingConventions

~/.salesforce

Build Query

Load Result Set

Similar CRUD

Demo

what does it look like?

Zoo.all( :age.gt => 30, :name.not => [“bob”, “jones”])

SELECT “age”, “name”, “description”FROM “zoos”WHERE (“age” > 30) AND (“name” NOT IN (“bob”, “jones”))

Zoo.first.eql? Zoo.first#=> true

Zoo.all.map {|x| x.animals }how many queries?

2

we call thisstrategic eager loading.

lazy loading

include DataMapper::Resource

property :id, Fixnum, :serial => true property :title, String property :body, Text, :lazy => trueend

class Post

posts = Post.all

SELECT “id”, “title”FROM “posts”

return two objectsids 1 and 2

SELECT “body”FROM “posts”WHERE (“id” IN (1,2))

posts.first.body

SELECT “body”FROM “posts”WHERE (“id” IN (1,2))

posts.map{|x| x.body}

lazy loaded grouping

include DataMapper::Resource

property :id, Fixnum, :serial => true property :title, String, :lazy => [:details] property :body, Text, :lazy => [:details]end

class Post

you can go off the golden path

class Post include DataMapper::Resource property :title, String

repository(:legacy) do property :title, String, :field => “T1tLz” endend

Post.all(:repository => :legacy)

repository(:legacy) do Post.allend

Post.all

Post.all(:repository => :default)

repository(:default) do Post.allend

repository(:legacy).adapter. resource_naming_convention = DM:: NamingConventions:: Underscored

naming conventions

AndPluralized

repository(:legacy).adapter. resource_naming_convention = lambda do |klass| “tbl#{klass.camel_case}” end

naming conventions

default repositoryclass Post include DataMapper::Resource def self.default_repository_name :legacy endend

import data

Post.copy(:legacy, :default)

Post.copy(:legacy, :default, :created_at.gt => Date.today - 365)

1.0

import dataclass Post property :title, String

repository(:legacy) do property :title, String, :field => “TIT13” endend

custom types

primitivesTrueclass, string, text, float, fixnum,

bigdecimal, datetime, date, object, class

custom types

class Post include DataMapper::Resource property :title, String property :author, FullName property :details, Csvend

class FullName < DM::Type primitive String size 100

def self.load(str) str.split(“, ”).reverse end

def self.dump(ary) ary.reverse.join(“, ”) endend

class Csv < DM::Type primitive String size 65355

def self.load(str) FasterCSV.parse(value) end

def self.dump(ary) FasterCSV.generate do |csv| ary.each {|line| csv << line} end endend

Post.create!( :title => “New Post”, :author => [“Yehuda”, “Katz”], :metadata => [ [“Some”, “Sample”, “Data”], [“More”, “Sample”, “Data”] ])

Title

Author

Metadata

“New Post”

“Katz, Yehuda”

“Some,Sample,Data\nMore,Sample,Data\n”

in the database

and it’s lazy-parsed

custom stores

stores are uris

mysql://user@localhost

setting up

DataMapper.setup( :default, “mysql://user@localhost”)

database.yml

development: default: adapter: mysql database: app_dev user: person password: sekrit

database.yml

legacy: adapter: sqlite3 database: config/l3g.db

yaml:///fixtures

1.0

ssh+yaml://fixtures.engineyard.com/

fixtures

1+

database.ymltest: default: adapter: yaml database: app_test.db legacy: adapter: yaml database: l3g_test.db

making fixtures

Post.copy(:default, :fixtures)

rake db:copy_fixtures

validations

class Product include DataMapper::Resource property :title, String property :price, String, :nullable => false, :validation_context => :purchaseend

validates_length_of

validates_presence_of

valid_for_purchase?

class Product include DataMapper::Resource property :title, String property :number, String, :format => /\d{3}-[a-zA-Z]{9}-0/end validates_format_of

class Product include DataMapper::Resource property :title, String property :number, String, :format => proc {|n| n.split(“-”).size == 2}

end

validates_format_of

class Product include DataMapper::Resource property :title, String property :number, String, :length => 2..10, :validation_context => :import

end

validates_length_of

valid_for_import?save(:import)

class Product include DataMapper::Resource property :title, String property :number, String,

end valid_for_import?

validates_length_of :number, :in => (2..10), :when => :import

thank you.

any questions?

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