De vuelta al pasado con SQL y stored procedures

Volver al futuro con SQL
y stored procedures

Norman Clarke
Business Vision Ruby Labs
@compay

Wednesday, November 9, 11

Lo que les espera...

• Características, ventajas y desventajas de
stored procedures
• Una librería experimental basada en stored
procedures
• Stored procedures vs. ORM


Stored Procedures
programación "real" con SQL


postgres=# select greeting();

greeting
-------------
hello world!

(1 row)


1 CREATE FUNCTION greeting()
2 RETURNS TEXT AS $$
3 BEGIN
4 RETURN 'hello world!';
5 END;
6 $$ LANGUAGE 'plpgsql';


declare
begin
select ...
if ... then
update ...
else
while ... loop
...
end loop;
end if;
return ...;
end;

¿Cuántas funciones?
Postgres: 2333
Lua: 135


Ventajas


Cacheo automático
de consultas


Menos coordinación
entre la BD y Ruby

O Java, Python, Perl, PHP, etc.


Encapsulación del esquema

Stored
Esquema Ruby
Procedures


Toda la lógica de negocios
en SQL


No hagan eso por favor


Squirm
github.com/bvision/squirm


Squirm

• Azúcar sintáctico para la gema "pg"
• Connection pool básico
• Stored procedures como procs o lambdas


1 Squirm.connect host: "localhost"
2 Squirm.transaction do
3 Squirm.exec "SELECT ..." do |result|
4 result.to_a
5 end
6 Squirm.rollback
7 end


1 Squirm do
2 connect host: "localhost"
3 transaction do
4 exec "SELECT ..." do |result|
5 result.to_a
6 end
7 rollback
8 end
9 end


1 Squirm do
2 exec "CREATE FUNCTION ..."
3 proc = procedure "greeting"
4 proc.call "Juan"
5 #=> "¡hola Juan!"
6 end


1 class Foo
2
3 @@bar = Procedure.load "bar"
4
5 def bar(*args)
6 @@bar.call(*args)
7 end
8 end
9
10 foo = Foo.new
11 foo.bar("hello")

GET followers/ids
GET friends/ids
GET lists/all
GET favorites
GET statuses/home_timeline
GET statuses/mentions
GET statuses/user_timeline
GET direct_messages


SELECT followers.ids()
SELECT friends.ids()
SELECT lists.all()
SELECT favorites()
SELECT statuses.home_timeline()
SELECT statuses.mentions()
SELECT statuses.user_timeline()
SELECT direct_messages()


Squirm Model
github.com/bvision/squirm_model


Squirm Model

• Generador de tablas, procedures
• SQL "scaffolding"
• Active Model


$ squirm table person id email birth_date access_time bio

1 CREATE TABLE "person" (
2 "id" SERIAL NOT NULL PRIMARY KEY,
3 "email" VARCHAR(64) NOT NULL UNIQUE,
4 "birth_date" DATE,
5 "access_time" TIMESTAMP WITH TIME ZONE,
6 "bio" TEXT
7 );


$ squirm table person id created_at

1 CREATE TABLE "person" (
2 "id" SERIAL NOT NULL PRIMARY KEY,
3 "created_at" TIMESTAMP WITH TIME ZONE NOT NULL
4 );
5
6 CREATE OR REPLACE FUNCTION "update_person_created_at_timestamp"
7 RETURNS TRIGGER AS $$
8 BEGIN
9 NEW.created_at = NOW();
10 RETURN NEW;
11 END;
12 $$ LANGUAGE 'plpgsql';
13
14 CREATE TRIGGER "update_person_created_at_timestamp"
15 BEFORE INSERT ON "person"
16 FOR EACH ROW EXECUTE PROCEDURE "update_person_created_at_time


$ squirm table person id email --api

CREATE TABLE "person" ...
CREATE SCHEMA "person" ...
CREATE FUNCTION "person.get" ...
CREATE FUNCTION "person.create" ...
CREATE FUNCTION "person.update" ...
CREATE FUNCTION "person.delete" ...


1 class Person
2 extend Squirm::Model
...
3 validates_presence_of :name
4 end
5
6 Person.create(...)
7 @person = Person.find(1)
8 @person.valid?
9 @person.to_json
10 redirect_to @person

1 class Person
2 extend Squirm::Model
3
4 sample do |s|
5 s.id = 1
6 s.name = "Juan Fulano"
7 end
8
9 validates_presence_of :name
10 end


1 class PersonTest < Test::Unit::TestCase
2 def test_create
3 assert Person.create(Person.sample)
4 end
5 end


1 Squirm do
2 connect host: "localhost"
3
4 exec Person.to_ddl
5
6 Person.finalize
7
8 p = Person.create name: "John"
9 p.update name: "Johnny"
10 p.delete
11 end

Benchmarks

ROFLSCALE

0 7.5 15 22.5 30

Squirm Model ActiveRecord


¿Por qué no usar un
ORM?


Usen los ORM
• Active Record
• DataMapper
• Sequel
• otros


Pero conozcan
sus defectos


Exhibition.all(
:run_time.gt => 2,
:run_time.lt => 5
)

run_time > 1 AND run_time < 5

...you might be wondering how we can specify conditions
beyond equality without resorting to SQL.Well, thanks to some
clever additions to the Symbol class, it’s easy!


table = Product.arel_table
Product.where(
table[:price].eq(2.99).
or(table[:name].matches("%foo"))
).to_sql

#=> "WHERE price = 2.99 OR name LIKE '%foo'"

railscasts.com/episodes/215-advanced-queries-in-rails-3


SQL (mal) generado


La abstracción diﬁculta
el uso de features
avanzados


Los stored procedures
ofrecen una alternativa
interesante


"Pensemos diferente"


Nihil sub sole novum


Postgres y MySQL están
muy desaprovechados


No usemos
abstracciones
innecesarias


¡Gracias!


Gracias, fotógrafos
Obelisco: ﬂickr.com/photos/budgetplaces/4173902613/
Matz: ﬂickr.com/photos/rrrodrigo/2394122680/


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