DataMapper

datamapper the persistence framework

who am I?

(Booth 501)

DataMapper

datamapper

object relational mapper

like activerecord

like activerecord ★ DB adapters ★ many-to-many ★ migrations ★ -through ★ associations ★ polymorphic ★ one-to-one ★ lifecycle events ★ one-to-many ★ sti ★ many-to-one ★ etc.

drops into Rails 1.0

(or merb) 0.9

architecture Application Merb Rails DataMapper Adapters DO.rb YAML IMAP Data Stores

some caveats

work in progress 0.9 1.0

be prepared for code

why did we build it?

identity map

Foo[1] Foo id = 1 Foo[1] ...

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

loadedset

foo.all Foo Foo Foo Foo Foo Foo id = 1 id = 2 id = 3 id = 4 id = 5 id = 6 ... ... ... ... ... ... LoadedSet

composite keys

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

legacy data

naming conventions (yours)

naming conventions underscored foo::barBaz => foo/bar_baz

naming conventions underscoredandpluralized foo::barBaz => foo_bar_bazs

naming conventions underscoredandpluralizedwithoutmodule foo::barBaz => bazs

naming conventions yaml foo::Bar => foo/bars.yaml

support for multiple databases (even in the same model)

Post.all(:repository => :legacy) Post.all # :repository => :default

prepared statements 1.0

custom types

embedded values 1.0

Employments Employment id: int id<Integer> person_id: int person<Person> start: date end: date start<Date> salary_amt: dec end<Date> salary_cur: char salary<Money>

declared properties property :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 Connection Connection Connection Connection Connection Pool create_command “select * from foos where id = ?” 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 Naming Conventions ~/.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 this strategic eager loading.

lazy loading

class Post include DataMapper::Resource property :id, Fixnum, :serial => true property :title, String property :body, Text, :lazy => true end

posts = Post.all SELECT “id”, “title” FROM “posts”

return two objects ids 1 and 2

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

posts.map{|x| x.body} SELECT “body” FROM “posts” WHERE (“id” IN (1,2))

lazy loaded grouping

class Post include DataMapper::Resource property :id, Fixnum, :serial => true property :title, String, :lazy => [:details] property :body, Text, :lazy => [:details] end

you can go off the golden path

class Post include DataMapper::Resource property :title, String repository(:legacy) do property :title, String, :field => “T1tLz” end end

Post.all(:repository => :legacy) repository(:legacy) do Post.all end

Post.all Post.all(:repository => :default) repository(:default) do Post.all end

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

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

default repository class Post include DataMapper::Resource def self.default_repository_name :legacy end end

import data Post.copy(:legacy, :default) Post.copy(:legacy, :default, :created_at.gt => Date.today - 365) 1.0

import data class Post property :title, String repository(:legacy) do property :title, String, :field => “TIT13” end end

custom types

primitives Trueclass, string, text, ﬂoat, ﬁxnum, bigdecimal, datetime, date, object, class

custom types class Post include DataMapper::Resource property :title, String property :author, FullName property :details, Csv end

class FullName < DM::Type primitive String size 100 def self.load(str) str.split(“, ”).reverse end def self.dump(ary) ary.reverse.join(“, ”) end end

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 end end

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

in the database Title “New Post” Author “Katz, Yehuda” “Some,Sample,Datan Metadata More,Sample,Datan”

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.yml test: 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, validates_length_of :nullable => false, :validation_context => validates_presence_of :purchase end 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} validates_format_of end

class Product include DataMapper::Resource property :title, String property :number, String, :length => 2..10, :validation_context => validates_length_of :import valid_for_import? save(:import) end

class Product include DataMapper::Resource property :title, String property :number, String, validates_length_of :number, :in => (2..10), :when => :import end valid_for_import?

thank you.

any questions?

</railsconf>

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http://schulty.com	8
http://www.linkedin.com	7
http://substantiality.net	5
http://www.ofelio.com	4
http://datamapper.github.com	4
http://sensimevanidus.tumblr.com	3
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http://www.techgig.com	1
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http://0.0.0.0:4331	1
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DataMapper

by Yehuda Katz

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DataMapper

by Yehuda Katz

Accessibility

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DataMapper Presentation Transcript

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