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,Data\\n
Metadata
More,Sample,Data\\n”

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>