Life without ORM

Sergey Protko

InTouch Health

Life Without ORM

Sergey Protko

ORM: The Vietnam War of Computer Science

http://blogs.tedneward.com/post/the-vietnam-of-computer-science/

Object/Relational Impedance Mismatch

  • Flat vs Hierarchical
  • References
  • Encapsulation

In memory structure

author_id post_id post_title post_body post_author_id post_created_at
67 34 Some title just having fun 67 2019-05-03T14:53:41.670300
67 45 GoT 8 season it sucks 67 2019-05-03T23:26:41.670300
67 56 Chernobyl  nice, HBO 67 2019-05-28T23:26:41.670300
67 58 HBO cancelling subscription 67 2019-05-28T23:26:41.670300
68 42 Continious delivery Companies want to deliver frequently 68 2019-05-28T23:26:41.670300
68 57 DevOps missunderstanding 68 2019-05-28T23:26:41.670300
68 87 Trunk based development TBD 68 2019-05-28T23:26:41.670300
68 94 Yet another post I too lazy to think about text 68 2019-05-28T23:26:41.670300
68 98 And another one Hodor hodor 68 2019-05-28T23:26:41.670300

Relational World

$resultSet = $db->fetchAll($sql, [$params], [$paramTypes]);

$authorMapper = mapper([
    'id' => pk('author_id'),
    'name' => field('author_name'),
]);

$result = array_reduce($resultSet, $authorMapper->extend([
    'posts' => many([
        'id' => pk('post_id'),
        'title' => field('post_title'),
        'body' => field('post_body'),
        'author' => one($authorMapper),
        'createdAt' => field('post_created_at', 'datetimetz_immutable')
    ])
]));

Relatively easy to solve

Query Builders

mostly needed for query introspection*

Query Builders

mostly needed for query introspection*

const selectUser = (userId: string) =>
  sql`SELECT u.id, u.name, age(u.birthDate) as age FROM users WHERE u.id=${userId}`

*and parameters binding...

Flat vs Hierarchical

CREATE TABLE customers (
    customer_id integer PRIMARY KEY,
    referral_id integer 
        REFERENCES customers (customer_id)
)

References

$post = $author->posts()->first();
$postAuthor = $post->author();

assert($postAuthor === $author);

Relations

CREATE TABLE authors (
    author_id integer PRIMARY KEY,
    name text NOT NULL
);

CREATE TABLE posts (
    post_id integer PRIMARY KEY,
    image_url text NOT NULL,
    author_id integer NOT NULL REFERENCES authors
);

Encapsulation

Encapsulation

class Customer
{
    private int $id;
    private string $name;
    private ?Customer $referral;

    public function getId(): int
    {
        return $this->id;
    }
    
    public function setName(string $name): void
    {
        $this->name = $name;
    }

    public function getName(): string
    {
        return $this->name;
    }

    public function setReferral(Customer $referral): void
    {
        $this->referral = $referral;
    }

    public function getReferral(): ?Customer
    {
        return $this->referral;
    }
}

This is not what I meant by OOP

NO ORM

Means no relational DB

NO ORM

Means no relational DB

General Purpose ORM

Atlas ORM

Most valuable ORM features

  • Schema generation

  • Mapping of data types

  • Lazy Load

  • Automatic transaction management

  • Query Builder

  • Generate CRUD

Most valuable ORM features

  • Schema generation (DBAL)

  • Mapping of data types (DBAL)

  • Lazy Load

  • Automatic transaction management

  • Query Builder 

  • Generate CRUD

class User
{
    private $id;
    private $email;
    private $emailConfirmationToken;
    private $changedEmail;
    private $password;
    private $passwordResetToken;
    private $name;
    private $profilePic;
    private $birthDate;
}

Transaction Boundaries

class User
{
    private $id;
    private $email;
    private $emailConfirmationToken;
    private $changedEmail;
    private $password;
    private $passwordResetToken;
    private $name;
    private $profilePic;
    private $birthDate;
}

Transaction Boundaries

class User
{
    private $id;
    private $email;
    private $emailConfirmationToken;
    private $changedEmail;
    private $password;
    private $passwordResetToken;
    private $name;
    private $profilePic;
    private $birthDate;
}

Transaction Boundaries

class User
{
    private $id;
    private $email;
    private $emailConfirmationToken;
    private $changedEmail;
    private $password;
    private $passwordResetToken;
    private $name;
    private $profilePic;
    private $birthDate;
}

Transaction Boundaries

Automatic transaction management

$user = $userRepository->find($id);

$user->changePassword($oldPassword, $newPassword, $encoder);

$em->flush();
UPDATE users
SET
    password=?
WHERE 
    id=?

Lazy Load

class Post
{
    private $id;
    private $photo;
    private $postedAt;
    private $description;
    private $tags;        // collection
    private $author;      // reference
    private $reactions;   // collection
    private $comments;    // collection
}

Lazy Load

class Post
{
    private $id;
    private $photo;
    private $postedAt;
    private $description;
    private $tags;        // collection
    private $author;      // reference
    private $reactions;   // collection
    private $comments;    // collection
}

New feature

Model

Aggregates

Aggregates

~= document

{
    post(id: "1000") {
        id
        photo {
           ...photoFields
        }
        description
        comments(limit: 1) {
            ...commentFields
        }
        reactions {
            ...reactionFields
        }
        author {
            ...profileFields
        }
    }
}

Application-side Joins

N+1 queries

Logical transactions

Split process into multiple logical transactions

Saga Pattern

Domain Events!

Eventual Consistency!

Message driven architecture

Pipelines

https://www.youtube.com/watch?v=YGhS8VQpS6s

https://dzone.com/articles/applying-brooks-law-to-lines-of-communication-and

Split into teams

public function get(string $id, \Closure $fn)
{
    $entity = $this->doctrineRepository->find($id);
    if (!$entity) {
        throw new SomeEntityNotFound();
    }
    $aggregate = $this->automapper->map($entity, SpecificAggregate::class);
    $fn($aggregate);
    $this->automapper->map($aggregate, $entity);
}

You could slice project later

Microservices

are about risk management

https://docs.microsoft.com/en-us/dotnet/standard/microservices-architecture/architect-microservice-container-applications/microservice-based-composite-ui-shape-layout

What about CRUD?

https://cqrs.wordpress.com/documents/task-based-ui/

Task Based UI

https://cqrs.wordpress.com/documents/task-based-ui/

Most efficient way to write CRUD

is to write nothing

Most efficient way to write CRUD

is to write nothing

It's easy to blame tools for project failure

Thank you!