Database Design Patterns
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Database Design Patterns

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This session introduces most well known design patterns to build PHP classes and objects that need to store and fetch data from a relational databases. The session will describe the difference between ...

This session introduces most well known design patterns to build PHP classes and objects that need to store and fetch data from a relational databases. The session will describe the difference between of the Active Record, the Table and Row Data Gateway and the Data Mapper pattern. We will also examine some technical advantages and drawbacks of these implementations. This talk will expose some of the best PHP tools, which ease database interactions and are built on top of these patterns.

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Database Design Patterns Database Design Patterns Presentation Transcript

  • Enterprise Database Design Patterns in PHP Hugo Hamon – OSIDays 2011
  • By Martin Fowler§  Table Module§  Transaction Script§  Row Data Gateway§  Table Data Gateway§  Active Record§  Data Mapper§  Unit of Work§  Identity Map§  Data Transfer Object§  …
  • Table Data Gateway
  • « An object that acts as a Gateway toa database table. One instancehandles all the rows in the table. » Martin Fowler  
  • Same asData Access Object Martin Fowler  
  • CRUD
  • $table = new OrderGateway(new Connection(...));$table->insert(XX123456789, 358.80, unpaid);$table->update(42, XX123456789, 358.80, paid);$table->delete(42);
  • class OrderGateway{ private $conn; public function __construct(Connection $conn) { $this->conn = $conn; }}
  • class OrderGateway{ public function insert($reference, $amount, $status) { $query = INSERT INTO orders (reference, amount,status) VALUES (?, ?, ?); $data = array($reference, $amount, $status); $this->conn->executeQuery($query, $data); return $this->conn->lastInsertId(); }}
  • class OrderGateway{ public function update($pk, $ref, $amount, $status) { $query = UPDATE orders SET reference = ?, amount= ?, status = ? WHERE id = ?; $data = array($ref, $amount, $status, $pk); return $this->conn->executeQuery($query, $data); }}
  • class OrderGateway{ public function delete($pk) { return $this->conn->executeQuery( DELETE FROM orders WHERE id = ?, array($pk) ); }}
  • Finders
  • $orders = $table->findAll();$orders = $table->findPaidOrders();$orders = $table->findUnpaidOrders();$orders = $table->findBy(array( status => paid, amount => 250.00));$order = $table->find(42);$order = $table->findOneBy(array(reference => ...));
  • class OrderGateway{ public function findAll() { $query = SELECT * FROM orders; return $this->conn->fetchAll($query); } public function find($pk) { $rs = $this->conn->findBy(array(id => $pk)); return 1 === count($rs) ? $rs[0] : false; }}
  • public function findBy(array $criteria){ $where = array(); foreach ($criteria as $field => $value) { $where[] = sprintf(%s = ?); } $q = sprintf( SELECT * FROM orders WHERE %s, implode( AND , $where) ); return $this->conn->fetchAll($q, array_values($criteria));}
  • public function findPaidOrders(){ return $this->findBy(array(status => paid));}public function findUnpaidOrders(){ return $this->findBy(array(status => unpaid));}
  • When to use it?
  • Row Data Gateway
  • « An object that acts as a Gateway toa single record in a data source. Thereis one instance per row. » Martin Fowler  
  • CRUD
  • class Order{ private $id; private $reference; private $amount; private $vat; private $total; private $createdAt; // Getters and setters for each property // ...}
  • $conn = new Connection(...);$order = new OrderGateway();$order->setReference(XX12345678);$order->setAmount(300.00);$order->setVat(58.80);$order->setTotal(358.80);$order->setCreatedAt(new DateTime());$order->insert($conn);
  • class OrderGateway{ public function insert(Connection $conn) { $query = INSERT INTO orders (reference, amount, vat,total, created_at) VALUES (?, ?, ?, ?, ?); $data = array( $this->reference, $this->amount, $this->vat, $this->total, $this->createdAt->format(Y-m-d H:i:s) ); $conn->executeQuery($query, $data); $this->id = $conn->lastInsertId(); }}
  • Finders
  • OrderFinder::setConnection($conn);$order = OrderFinder::findByReference(XX12345678);echo sprintf(%01.2f euros, $order->getTotal());
  • class OrderFinder{ static public function findByReference($reference) { $query = SELECT * FROM orders WHERE reference = ?; $rs = static::getConnection() ->fetchSingle($query, array($reference)) ; return $rs ? OrderGateway::load($rs) : false; }}
  • class OrderGateway{ static public function load(array $rs) { $order = new OrderGateway($rs[id]); $order->setReference($rs[reference]); $order->setAmount($rs[amount]); $order->setVat($rs[vat]); $order->setTotal($rs[total]); $order->setCreatedAt(new DateTime($rs[created_at])); return $order; }}
  • OrderFinder::setConnection($conn);$orders = OrderFinder::findMostExpensiveOrders(10);foreach ($orders as $order) { echo $order->getReference(), "n"; echo sprintf(%01.2f euros, $order->getTotal()), "n"; echo "n-----n";}
  • class OrderFinder{ static public function findMostExpensiveOrders($limit) { $orders = array(); $query = SELECT * FROM orders ORDER BY total DESC LIMIT ?; $rs = static::getConnection()->fetchAll($query, array($limit)); foreach ($rs as $data) { $orders[] = OrderGateway::load($data); } return $orders; }}
  • When to use it?
  • Active Record
  • « An object that wraps a row in adatabase table or view, encapsulatesthe database access, and addsdomain logic on that data. » Martin Fowler  
  • Active Record =Row Data Gateway + Business Logic
  • Active Record =Data + Behaviors
  • Active Record =Properties + Methods
  • class Order{ private $id; private $reference; private $amount; private $vat; private $vatRate; private $total; private $createdAt; private $status; private $isPaid; // Getters and setters for each property // ...}
  • class Order{ public function __construct($id = null) { if (null !== $id) { $this->id = $id; } $this->vatRate = 0.00; $this->vat = 0.00; $this->amount = 0.00; $this->total = 0.00; $this->isPaid = false; $this->status = processing; $this->createdAt = new DateTime(); }}
  • $conn = new Connection(...);$order = new Order();$order->setReference(XX12345678);$order->setAmount(300.00);$order->setVatRate(0.196);$order->applyDiscount(20.00);$order->updateTotal();$order->save($conn);
  • class Order{ public function applyDiscount($discount) { $this->amount -= $discount; } public function updateTotal() { if ($this->vatRate) { $this->vat = $this->amount * $this->vatRate; } $this->total = $this->amount + $this->vat; }}
  • class Order{ public function isPaid() { return $this->isPaid; } public function setPaid() { $this->isPaid = true; }}
  • class Order{ public function isReadyForShipment() { return $this->isPaid() && complete == $this->status; } public function ship($address) { $this->doShipment($address); $this->status = shipped; }}
  • class OrderController{ public function confirmAction($reference) { $conn = $this->getDatabaseConnection(); $order = ...; $order->setPaid(); $order->save($conn); if ($order->isReadyForShipment()) { $order->ship(); return $this->view->render(ship.php, array(order => $order)); } return $this->view->render(pending.php, array(order => $order)); }}
  • Refactoring
  • abstract class ActiveRecord{ protected $fields = array(); abstract public function getTableName(); public function save(Connection $conn) { // insert or update $fields in the database } public function delete(Connection $conn) { // delete the object from the database }}
  • class Order extends ActiveRecord{ private $amount; abstract public function getTableName() { return tbl_orders; } public function setAmount($amount) { $this->amount = $amount; $this->fields[amount] = $amount; }}
  • When to use it?
  • Data Mapper
  • « A layer of Mappers that moves databetween objects and a databasewhile keeping them independent ofeach other and the mapper itself. » Martin Fowler  
  • « Man in the Middle »
  • http://martinfowler.com  
  • class OrderMapper{ private $conn; public function __construct(Connection $conn) { $this->conn = $conn; } public function store(Order $order) { // Execute the query to persist the object to the DB } public function remove(Order $order) { // Executes the query to remove the object to the DB }}
  • $order = new Order();$order->setReference(XX12345678);$order->setAmount(300.00);$order->setVatRate(0.196);$order->updateTotal();$conn = new Connection(mysql:host=localhost ...);$mapper = new OrderMapper($conn);$mapper->store($order);
  • class OrderMapper{ public function findAll() { $objects = array(); $query = SELECT id, reference, vat ... FROM orders; foreach ($this->conn->fetchAll($query) as $data) { $object = new Order($data[id]); $object->load($data); $objects[] = $object; } return $objects; }}
  • class OrderMapper{ public function find($pk) { $query = SELECT id, vat ... FROM orders WHERE id = ?; $object = false; if (false !== $data = conn->fetch($query, array($pk))) { $object = new Order($data[id]); $object->load($data); } return $object; }}
  • $conn = new Connection(mysql:host=localhost ...);$mapper = new OrderMapper($conn);$order = $mapper->find(42);$order->setAmount(399.00);$order->updateTotal();$mapper->store($order);
  • Unit testing
  • class OrderTest extends PHPUnit_Framework_TestCase{ public function testUpdateTotal() { $order = new Order(); $order->setAmount(299.00); $order->setVatRate(0.196); $order->updateTotal(); $this->assertEquals(58.60, $order->getVat()); $this->assertEquals(357.60, $order->getTotal()); }}
  • When to use it?
  • IdentityMap
  • « Ensures that each object getsloaded only once by keeping everyloaded object in a map. » Martin Fowler  
  • $conn = new Connection(mysql:host=localhost ...);$mapper = new OrderMapper($conn);$orderA = $mapper->find(42);$orderB = $mapper->find(42);$orderC = $mapper->find(42);// 3 SQL queries for getting the same object
  • The solution
  • class IdentityMap implements IdentityMapInterface{ private $entities; public function fetch($class, $pk) { $key = $this->getKey($class, $pk); if (isset($this->entities[$key])) { return $this->entities[$key]; } return false; }}
  • class IdentityMap implements IdentityMapInterface{ public function store(ValueObjectInterface $entity) { $key = $this->getKey($class, $entity->getId()); $this->entities[$key] = $entity; } private function getKey($class, $pk) { return $class.-.$pk; }}
  • class Order implements ValueObjectInterface{ private $id; private $reference; private $amount; // ... public function getId() { return $this->id; }}
  • class OrderMapper extends DatabaseMapper{ private $map; public function __construct(IdentityMap $map, ...) { parent::__construct($conn); $this->map = $map; }}
  • class OrderMapper extends DatabaseMapper{ public function store(Order $order) { parent::store($order); $this->map->store(Order, $object); }}
  • class OrderMapper extends DatabaseMapper{ public function find($pk) { if (false !== $object = $this->map->fetch($pk)) { return $object; } if (false !== $object = parent::find($pk)) { $this->map->store(Order, $object); } return $object; }}
  • $conn = new Connection(mysql:host=localhost ...);$mapper = new OrderMapper(new IdentityMap(), $conn);$orderA = $mapper->find(42); // Query$orderB = $mapper->find(42); // No query$orderB->setAmount(299.00);$orderB->setVatRate(0.196);$orderB->updateTotal();$mapper->store($orderB);$orderC = $mapper->find(42); // No query
  • Query Object
  • $query = Query::create() ->select(array(id, reference, amount, status)) ->from(orders) ->where(Criteria::equals(status, paid)) ->where(Criteria::greaterThan(amount, 2000)) ->where(Criteria::like(reference, XX123%)) ->orderBy(amount, desc) ->getSql();// SELECT id, reference, amount, status// WHERE status = ? AND amount > ? AND reference LIKE ?// ORDER BY amount DESC
  • class Criteria{ private $field; private $operator; private $parameters; public function __construct($field, $operator, $value) { $this->field = $field; $this->operator = $operator; $this->parameters[] = $value; }}
  • class Criteria{ static public function equal($field, $value, $vars) { return new Criteria($field, =, $vars); } static public function notEqual($field, $value, $vars) { return new Criteria($field, <>, $vars); }}
  • Custom Queries
  • class OrderQuery extends Query{ public function filterByPriority($amount) { return $this ->where(Criteria::equal(status, paid)) ->where(Criteria::greaterThan(amount, $amount)) ; } public function filterByReference($like) { return $this->where(Criteria::like(reference, $like)); }}
  • $query = OrderQuery::create() ->filterByPriority(2000) ->filterByReference(%567%) ->orderByAmount(DESC) ->getSql();
  • ORM Tools
  • Zend_DB Propel Doctrine 2.xPomm Doctrine 1.2
  • QuizzCan you guess the patterns?
  • $table = new Author();// New empty row$row = $table->createRow();// Insert a new row$row->firstName = Jules;$row->lastName = Verne;$row->save();
  • $pax1 = new Passenger(Hugo Hamon, 7B);$pax2 = new Passenger(John Smith, 3A);$aircraft = new Plane();$aircraft->setCapacity(120);$aircraft->addPassenger($pax1);$aircraft->addPassenger($pax2);$aircraft->save();$pax2->changeSeat(2C);$pax2->save();$aircraft->isAvailableSeat(3A) ? Yes : No;
  • $post = new BlogPost();$post->setTitle(My First Blog Post);$post->setBody(Some content...);$author = new Author();$author->setName(Hugo Hamon);$author->addPost($post);$em->persist($user);$em->persist($post);$em->flush();
  • $data = array( first_name => Jules, last_name => Vernes,);$table = new AuthorTable();$table->insert($data);
  • Conclusion
  • By Martin Fowler§  Table Module§  Transaction Script§  Row Data Gateway§  Table Data Gateway§  Active Record§  Data Mapper§  Unit of Work§  Identity Map§  Data Transfer Object§  …
  • Ques&ons?   92-98, boulevard Victor Hugo 92 115 Clichy Cedex trainings@sensio.com (+33 (0)1 40 99 82 11) sensiolabs.com - symfony.com – trainings.sensiolabs.com