Theoretical question on Laravel here.
So Example of the caching I'd do is:
Article::with('comments')->remember(5)->get();
Ideally I'd like to have an event for Article updates that when the ID of a instance of that model (that's already cached) is updated I want to forget that key (even if it's the whole result of the query that's forgotten instead of just that one model instance), it is possible to do so?
If not is there some way to implement this reasonably cleanly?
So i was looking for an answer to the same question as OP but was not really satisfied with the solutions. So i started playing around with this recently and going through the source code of the framework, I found out that the remember() method accepts second param called key and for some reason it has not been documented on their site (Or did i miss that?).
Now good thing about this is that, The database builder uses the same cache driver which is configured under app/config/cache.php Or should i say the same cache system that has been documented here - Cache. So if you pass min and key to remember(), you can use the same key to clear the cache using Cache::forget() method and in fact, you can pretty much use all the Cache methods listed on the official site, like Cache::get(), Cache::add(), Cache::put(), etc. But i don't recommend you to use those other methods unless you know what you're doing.
Here's an example for you and others to understand what i mean.
Article::with('comments')->remember(5, 'article_comments')->get();
Now the above query result will be cached and will be associated with the article_comments key which can then be used to clear it anytime (In my case, I do it when i update).
So now if i want to clear that cache regardless of how much time it remembers for. I can just do it by calling Cache::forget('article_comments'); and it should work just as expected.
Hope this helps everyone :)
I think a good way to do is like this:
$value = Cache::remember('users', $minutes, function()
{
return DB::table('users')->get();
});
and then use Model Observers to detect the event of updating the model
class UserObserver {
public function saving($model)
{
//
}
public function saved($model)
{
// forget from cache
Cache::forget('users');
}
}
User::observe(new UserObserver);
Currently there are no easy way. However I found this workaround, which so far worked for me.
First you have to extend Illuminate\Database\Query\Builder.
<?php
class ModifiedBuilder extends Illuminate\Database\Query\Builder {
protected $forgetRequested = false;
public function forget()
{
$this->forgetRequested = true;
}
public function getCached($columns = array('*'))
{
if (is_null($this->columns)) $this->columns = $columns;
list($key, $minutes) = $this->getCacheInfo();
// If the query is requested ot be cached, we will cache it using a unique key
// for this database connection and query statement, including the bindings
// that are used on this query, providing great convenience when caching.
$cache = $this->connection->getCacheManager();
$callback = $this->getCacheCallback($columns);
if($this->forgetRequested) {
$cache->forget($key);
$this->forgetRequested = false;
}
return $cache->remember($key, $minutes, $callback);
}
}
Then you have to create new class which extends Eloquent Model.
<?php
class BaseModel extends Eloquent {
protected function newBaseQueryBuilder() {
$conn = $this->getConnection();
$grammar = $conn->getQueryGrammar();
return new ModifiedBuilder($conn, $grammar, $conn->getPostProcessor());
}
}
Now when creating Eloquent Models, instead of extending Eloquent Models extend newly created BaseModel.
Now you can remember query result as usual.
YourModel::remember(10)->get();
When you want to discard the cached result all you have to do is
YourModel::forget()->get();
If you remember the result previously, after clearing the cached result, model will continue to remember the result for that amount of time.
Hope this helps.
I was testing for debug mode. So I found that if you put a test for app.debug in a constructor you are able to clear the cache associated with a key. Saves you having to duplicate the code for every function.
class Events {
public function __construct() {
if (\Config::get('app.debug')) {
Cache::forget('events');
}
}
public static function all() {
$events = \DB::table('events as e')
->select('e.*')
->where('enabled', 1)
->remember(30, 'events')
->get();
return $events;
}
}
I'm working in an PHP application, and I'd like to be able to instantiate an object, but I need it to get instantiated only with SOME of it's properties, not all of them. Eg.
class User {
public function __construct() {
$this->user_id = 0;
$this->name = '';
$this->profile = array();
//...many other members here
}
}
Every time I instantiate this object it brings many collections of data, (for example, it brings all it's "profile" properties and so on). And this is sometimes not the wanted behavior because, let's say I need to use only the name of the user, why having in memory all the rest of the properties? But in other cases, I will need them all right away.
Some ideas:
I could create another class that extends User, and in the constructor method unset any unwanted properties. However, I'm looking for a more reusable way, so I can do the same with some other objects in my application.
I could take the properties out of the constructor method, but this would probably force me to change the core of the application (classes above User class), and alter many things in the application.
Is there a more reusable way like using an standard intermediary class or some design pattern?
Thank you.
The Keywords you are looking for are eager loading vs lazy loading.
In Short:
Eager Loading is what you are doing at the Moment: Once an object is created, you are loading all related objects and attributes, no matter how Long it takes.
Lazy loading is the opposite: There you will ONLY load Information, when it is required. (The Moment, it is really accessed)
--
A (very Basic) implementation of both would look like the example bellow.
//Data Model
abstract class UserModel{
protected $userData = null;
protected $userPosts = null;
protected function loadUserData(){
//do whatever required and store in $result
$this->userData = $result;
}
protected function loadUserPosts(){
//do whatever required and store in $result
$this->userPosts = $result;
}
public abstract function getUserData();
public abstract function getUserPosts();
}
//Eager Loading
class EagerUserModel extends UserModel {
public function __construct() {
$this->loadUserData()
$this->loadUserPosts();
}
public function getUserData(){
return $this->userData;
}
public function getUserPosts(){
return $this->userPosts;
}
}
//Lazy Loading
class LazyUserModel extends UserModel {
public function __construct() {
//do nothing
}
public function getUserData(){
if ($this->userData == null){
$this->loadUserData();
}
return $this->userData;
}
public function getUserPosts(){
if ($this->userPosts== null){
$this->loadUserPosts();
}
return $this->userPosts;
}
}
The Example will allow BOTH ways. However you could implement either eager or lazy loading within a single class, if you dont want to have the "choice", of which type to use.
Eager Loading has the Advantage that EVERY Information is "just there". Lazy Loading however requires a more complex architecture. To load the "UserPosts", you might require additional data about the user, which means you have to load the UserData first. This is something you Need to take into account!
So, Lazy loading is always faster?
No! That's the pitfall. Imagine, you have a class with 10 Attributes. If you are loading every Attribute in a lazy way, that would require 10 SQL-Queries to be fired (SELECT Name FROM user..., SELECT email FROM user... and so on). Doing this in an Eager way, would allow you to run only ONE Query: Select Name, email FROM user....
You have to find the Balance between both methods. Are Foreign Objects tightly Coupled? (I.e. user <-> Group)? -> Load Eager. Are foreign objects loosely coupled (User -> Posts on Image 545458) -> Load lazy.
Also Note, that this is an extreme example (100% eager vs 100% lazy). In practice, you may want to load some things eager (user data, Group allocation), and others lazy (comments, Group permissions) - You cant create a own Extension of the base class for every usecase. However having a "BaseClass" is always a good idea, because it gives you flexibility, whenever another implementation is required.
One way to go about it would to create a base-class that contains as little specialization as possible for it to work. Extending the base class and incrementally adding properties/features as needed would allow you to control what gets added.
This would conform to generally accepted object-oriented design patterns.
If you have entity written properly, I prefer to keep it and not to be worry about some empty properties, if the entity keeps its consistent state missing some values. If you don't need them, don't use them. If your script is more complex or long time running, take care of destructing objects when you don't need them anymore.
If the entity can be generalized to more common entity and to be used as base class for other entity later, and makes it sense, then go this way. This would be more difficult way, because refactoring would be needed.
You can also use object composition, when user entity keeps only main user data and one of value will be prepared for another object named profile, for example:
class User {
public function __construct() {
$this->user_id = 0;
$this->name = '';
$this->profile = null;
}
public function hasProfile()
{
return $this->profile != null;
}
}
class Profile {
public function __construct() {
$this->profile_id = 0;
$this->userPrefOne = '';
//...other members here
}
}
// then
$user = new User();
if ($profileDataNeeded)
{
$user->profile = new Profile();
$user->profile->userPrefOne = 'something';
}
Preface: I'm attempting to use the repository pattern in an MVC architecture with relational databases.
I've recently started learning TDD in PHP, and I'm realizing that my database is coupled much too closely with the rest of my application. I've read about repositories and using an IoC container to "inject" it into my controllers. Very cool stuff. But now have some practical questions about repository design. Consider the follow example.
<?php
class DbUserRepository implements UserRepositoryInterface
{
protected $db;
public function __construct($db)
{
$this->db = $db;
}
public function findAll()
{
}
public function findById($id)
{
}
public function findByName($name)
{
}
public function create($user)
{
}
public function remove($user)
{
}
public function update($user)
{
}
}
Issue #1: Too many fields
All of these find methods use a select all fields (SELECT *) approach. However, in my apps, I'm always trying to limit the number of fields I get, as this often adds overhead and slows things down. For those using this pattern, how do you deal with this?
Issue #2: Too many methods
While this class looks nice right now, I know that in a real-world app I need a lot more methods. For example:
findAllByNameAndStatus
findAllInCountry
findAllWithEmailAddressSet
findAllByAgeAndGender
findAllByAgeAndGenderOrderByAge
Etc.
As you can see, there could be a very, very long list of possible methods. And then if you add in the field selection issue above, the problem worsens. In the past I'd normally just put all this logic right in my controller:
<?php
class MyController
{
public function users()
{
$users = User::select('name, email, status')
->byCountry('Canada')->orderBy('name')->rows();
return View::make('users', array('users' => $users));
}
}
With my repository approach, I don't want to end up with this:
<?php
class MyController
{
public function users()
{
$users = $this->repo->get_first_name_last_name_email_username_status_by_country_order_by_name('Canada');
return View::make('users', array('users' => $users))
}
}
Issue #3: Impossible to match an interface
I see the benefit in using interfaces for repositories, so I can swap out my implementation (for testing purposes or other). My understanding of interfaces is that they define a contract that an implementation must follow. This is great until you start adding additional methods to your repositories like findAllInCountry(). Now I need to update my interface to also have this method, otherwise, other implementations may not have it, and that could break my application. By this feels insane...a case of the tail wagging the dog.
Specification Pattern?
This leads me to believe that repository should only have a fixed number of methods (like save(), remove(), find(), findAll(), etc). But then how do I run specific lookups? I've heard of the Specification Pattern, but it seems to me that this only reduces an entire set of records (via IsSatisfiedBy()), which clearly has major performance issues if you're pulling from a database.
Help?
Clearly, I need to rethink things a little when working with repositories. Can anyone enlighten on how this is best handled?
I thought I'd take a crack at answering my own question. What follows is just one way of solving the issues 1-3 in my original question.
Disclaimer: I may not always use the right terms when describing patterns or techniques. Sorry for that.
The Goals:
Create a complete example of a basic controller for viewing and editing Users.
All code must be fully testable and mockable.
The controller should have no idea where the data is stored (meaning it can be changed).
Example to show a SQL implementation (most common).
For maximum performance, controllers should only receive the data they need—no extra fields.
Implementation should leverage some type of data mapper for ease of development.
Implementation should have the ability to perform complex data lookups.
The Solution
I'm splitting my persistent storage (database) interaction into two categories: R (Read) and CUD (Create, Update, Delete). My experience has been that reads are really what causes an application to slow down. And while data manipulation (CUD) is actually slower, it happens much less frequently, and is therefore much less of a concern.
CUD (Create, Update, Delete) is easy. This will involve working with actual models, which are then passed to my Repositories for persistence. Note, my repositories will still provide a Read method, but simply for object creation, not display. More on that later.
R (Read) is not so easy. No models here, just value objects. Use arrays if you prefer. These objects may represent a single model or a blend of many models, anything really. These are not very interesting on their own, but how they are generated is. I'm using what I'm calling Query Objects.
The Code:
User Model
Let's start simple with our basic user model. Note that there is no ORM extending or database stuff at all. Just pure model glory. Add your getters, setters, validation, whatever.
class User
{
public $id;
public $first_name;
public $last_name;
public $gender;
public $email;
public $password;
}
Repository Interface
Before I create my user repository, I want to create my repository interface. This will define the "contract" that repositories must follow in order to be used by my controller. Remember, my controller will not know where the data is actually stored.
Note that my repositories will only every contain these three methods. The save() method is responsible for both creating and updating users, simply depending on whether or not the user object has an id set.
interface UserRepositoryInterface
{
public function find($id);
public function save(User $user);
public function remove(User $user);
}
SQL Repository Implementation
Now to create my implementation of the interface. As mentioned, my example was going to be with an SQL database. Note the use of a data mapper to prevent having to write repetitive SQL queries.
class SQLUserRepository implements UserRepositoryInterface
{
protected $db;
public function __construct(Database $db)
{
$this->db = $db;
}
public function find($id)
{
// Find a record with the id = $id
// from the 'users' table
// and return it as a User object
return $this->db->find($id, 'users', 'User');
}
public function save(User $user)
{
// Insert or update the $user
// in the 'users' table
$this->db->save($user, 'users');
}
public function remove(User $user)
{
// Remove the $user
// from the 'users' table
$this->db->remove($user, 'users');
}
}
Query Object Interface
Now with CUD (Create, Update, Delete) taken care of by our repository, we can focus on the R (Read). Query objects are simply an encapsulation of some type of data lookup logic. They are not query builders. By abstracting it like our repository we can change it's implementation and test it easier. An example of a Query Object might be an AllUsersQuery or AllActiveUsersQuery, or even MostCommonUserFirstNames.
You may be thinking "can't I just create methods in my repositories for those queries?" Yes, but here is why I'm not doing this:
My repositories are meant for working with model objects. In a real world app, why would I ever need to get the password field if I'm looking to list all my users?
Repositories are often model specific, yet queries often involve more than one model. So what repository do you put your method in?
This keeps my repositories very simple—not an bloated class of methods.
All queries are now organized into their own classes.
Really, at this point, repositories exist simply to abstract my database layer.
For my example I'll create a query object to lookup "AllUsers". Here is the interface:
interface AllUsersQueryInterface
{
public function fetch($fields);
}
Query Object Implementation
This is where we can use a data mapper again to help speed up development. Notice that I am allowing one tweak to the returned dataset—the fields. This is about as far as I want to go with manipulating the performed query. Remember, my query objects are not query builders. They simply perform a specific query. However, since I know that I'll probably be using this one a lot, in a number of different situations, I'm giving myself the ability to specify the fields. I never want to return fields I don't need!
class AllUsersQuery implements AllUsersQueryInterface
{
protected $db;
public function __construct(Database $db)
{
$this->db = $db;
}
public function fetch($fields)
{
return $this->db->select($fields)->from('users')->orderBy('last_name, first_name')->rows();
}
}
Before moving on to the controller, I want to show another example to illustrate how powerful this is. Maybe I have a reporting engine and need to create a report for AllOverdueAccounts. This could be tricky with my data mapper, and I may want to write some actual SQL in this situation. No problem, here is what this query object could look like:
class AllOverdueAccountsQuery implements AllOverdueAccountsQueryInterface
{
protected $db;
public function __construct(Database $db)
{
$this->db = $db;
}
public function fetch()
{
return $this->db->query($this->sql())->rows();
}
public function sql()
{
return "SELECT...";
}
}
This nicely keeps all my logic for this report in one class, and it's easy to test. I can mock it to my hearts content, or even use a different implementation entirely.
The Controller
Now the fun part—bringing all the pieces together. Note that I am using dependency injection. Typically dependencies are injected into the constructor, but I actually prefer to inject them right into my controller methods (routes). This minimizes the controller's object graph, and I actually find it more legible. Note, if you don't like this approach, just use the traditional constructor method.
class UsersController
{
public function index(AllUsersQueryInterface $query)
{
// Fetch user data
$users = $query->fetch(['first_name', 'last_name', 'email']);
// Return view
return Response::view('all_users.php', ['users' => $users]);
}
public function add()
{
return Response::view('add_user.php');
}
public function insert(UserRepositoryInterface $repository)
{
// Create new user model
$user = new User;
$user->first_name = $_POST['first_name'];
$user->last_name = $_POST['last_name'];
$user->gender = $_POST['gender'];
$user->email = $_POST['email'];
// Save the new user
$repository->save($user);
// Return the id
return Response::json(['id' => $user->id]);
}
public function view(SpecificUserQueryInterface $query, $id)
{
// Load user data
if (!$user = $query->fetch($id, ['first_name', 'last_name', 'gender', 'email'])) {
return Response::notFound();
}
// Return view
return Response::view('view_user.php', ['user' => $user]);
}
public function edit(SpecificUserQueryInterface $query, $id)
{
// Load user data
if (!$user = $query->fetch($id, ['first_name', 'last_name', 'gender', 'email'])) {
return Response::notFound();
}
// Return view
return Response::view('edit_user.php', ['user' => $user]);
}
public function update(UserRepositoryInterface $repository)
{
// Load user model
if (!$user = $repository->find($id)) {
return Response::notFound();
}
// Update the user
$user->first_name = $_POST['first_name'];
$user->last_name = $_POST['last_name'];
$user->gender = $_POST['gender'];
$user->email = $_POST['email'];
// Save the user
$repository->save($user);
// Return success
return true;
}
public function delete(UserRepositoryInterface $repository)
{
// Load user model
if (!$user = $repository->find($id)) {
return Response::notFound();
}
// Delete the user
$repository->delete($user);
// Return success
return true;
}
}
Final Thoughts:
The important things to note here are that when I'm modifying (creating, updating or deleting) entities, I'm working with real model objects, and performing the persistance through my repositories.
However, when I'm displaying (selecting data and sending it to the views) I'm not working with model objects, but rather plain old value objects. I only select the fields I need, and it's designed so I can maximum my data lookup performance.
My repositories stay very clean, and instead this "mess" is organized into my model queries.
I use a data mapper to help with development, as it's just ridiculous to write repetitive SQL for common tasks. However, you absolutely can write SQL where needed (complicated queries, reporting, etc.). And when you do, it's nicely tucked away into a properly named class.
I'd love to hear your take on my approach!
July 2015 Update:
I've been asked in the comments where I ended up with all this. Well, not that far off actually. Truthfully, I still don't really like repositories. I find them overkill for basic lookups (especially if you're already using an ORM), and messy when working with more complicated queries.
I generally work with an ActiveRecord style ORM, so most often I'll just reference those models directly throughout my application. However, in situations where I have more complex queries, I'll use query objects to make these more reusable. I should also note that I always inject my models into my methods, making them easier to mock in my tests.
Based on my experience, here are some answers to your questions:
Q: How do we deal with bringing back fields we don't need?
A: From my experience this really boils down to dealing with complete entities versus ad-hoc queries.
A complete entity is something like a User object. It has properties and methods, etc. It's a first class citizen in your codebase.
An ad-hoc query returns some data, but we don't know anything beyond that. As the data gets passed around the application, it is done so without context. Is it a User? A User with some Order information attached? We don't really know.
I prefer working with full entities.
You are right that you will often bring back data you won't use, but you can address this in various ways:
Aggressively cache the entities so you only pay the read price once from the database.
Spend more time modeling your entities so they have good distinctions between them. (Consider splitting a large entity into two smaller entities, etc.)
Consider having multiple versions of entities. You can have a User for the back end and maybe a UserSmall for AJAX calls. One might have 10 properties and one has 3 properties.
The downsides of working with ad-hoc queries:
You end up with essentially the same data across many queries. For example, with a User, you'll end up writing essentially the same select * for many calls. One call will get 8 of 10 fields, one will get 5 of 10, one will get 7 of 10. Why not replace all with one call that gets 10 out of 10? The reason this is bad is that it is murder to re-factor/test/mock.
It becomes very hard to reason at a high level about your code over time. Instead of statements like "Why is the User so slow?" you end up tracking down one-off queries and so bug fixes tend to be small and localized.
It's really hard to replace the underlying technology. If you store everything in MySQL now and want to move to MongoDB, it's a lot harder to replace 100 ad-hoc calls than it is a handful of entities.
Q: I will have too many methods in my repository.
A: I haven't really seen any way around this other than consolidating calls. The method calls in your repository really map to features in your application. The more features, the more data specific calls. You can push back on features and try to merge similar calls into one.
The complexity at the end of the day has to exist somewhere. With a repository pattern we've pushed it into the repository interface instead of maybe making a bunch of stored procedures.
Sometimes I have to tell myself, "Well it had to give somewhere! There are no silver bullets."
I use the following interfaces:
Repository - loads, inserts, updates and deletes entities
Selector - finds entities based on filters, in a repository
Filter - encapsulates the filtering logic
My Repository is database agnostic; in fact it doesn't specify any persistence; it could be anything: SQL database, xml file, remote service, an alien from outer space etc.
For searching capabilities, the Repository constructs an Selector which can be filtered, LIMIT-ed, sorted and counted. In the end, the selector fetches one or more Entities from the persistence.
Here is some sample code:
<?php
interface Repository
{
public function addEntity(Entity $entity);
public function updateEntity(Entity $entity);
public function removeEntity(Entity $entity);
/**
* #return Entity
*/
public function loadEntity($entityId);
public function factoryEntitySelector():Selector
}
interface Selector extends \Countable
{
public function count();
/**
* #return Entity[]
*/
public function fetchEntities();
/**
* #return Entity
*/
public function fetchEntity();
public function limit(...$limit);
public function filter(Filter $filter);
public function orderBy($column, $ascending = true);
public function removeFilter($filterName);
}
interface Filter
{
public function getFilterName();
}
Then, one implementation:
class SqlEntityRepository
{
...
public function factoryEntitySelector()
{
return new SqlSelector($this);
}
...
}
class SqlSelector implements Selector
{
...
private function adaptFilter(Filter $filter):SqlQueryFilter
{
return (new SqlSelectorFilterAdapter())->adaptFilter($filter);
}
...
}
class SqlSelectorFilterAdapter
{
public function adaptFilter(Filter $filter):SqlQueryFilter
{
$concreteClass = (new StringRebaser(
'Filter\\', 'SqlQueryFilter\\'))
->rebase(get_class($filter));
return new $concreteClass($filter);
}
}
The ideea is that the generic Selector uses Filter but the implementation SqlSelector uses SqlFilter; the SqlSelectorFilterAdapter adapts a generic Filter to a concrete SqlFilter.
The client code creates Filter objects (that are generic filters) but in the concrete implementation of the selector those filters are transformed in SQL filters.
Other selector implementations, like InMemorySelector, transform from Filter to InMemoryFilter using their specific InMemorySelectorFilterAdapter; so, every selector implementation comes with its own filter adapter.
Using this strategy my client code (in the bussines layer) doesn't care about a specific repository or selector implementation.
/** #var Repository $repository*/
$selector = $repository->factoryEntitySelector();
$selector->filter(new AttributeEquals('activated', 1))->limit(2)->orderBy('username');
$activatedUserCount = $selector->count(); // evaluates to 100, ignores the limit()
$activatedUsers = $selector->fetchEntities();
P.S. This is a simplification of my real code
I'll add a bit on this as I am currently trying to grasp all of this myself.
#1 and 2
This is a perfect place for your ORM to do the heavy lifting. If you are using a model that implements some kind of ORM, you can just use it's methods to take care of these things. Make your own orderBy functions that implement the Eloquent methods if you need to. Using Eloquent for instance:
class DbUserRepository implements UserRepositoryInterface
{
public function findAll()
{
return User::all();
}
public function get(Array $columns)
{
return User::select($columns);
}
What you seem to be looking for is an ORM. No reason your Repository can't be based around one. This would require User extend eloquent, but I personally don't see that as a problem.
If you do however want to avoid an ORM, you would then have to "roll your own" to get what you're looking for.
#3
Interfaces aren't supposed be hard and fast requirements. Something can implement an interface and add to it. What it can't do is fail to implement a required function of that interface. You can also extend interfaces like classes to keep things DRY.
That said, I'm just starting to get a grasp, but these realizations have helped me.
I can only comment on the way we (at my company) deal with this. First of all performance is not too much of an issue for us, but having clean/proper code is.
First of all we define Models such as a UserModel that uses an ORM to create UserEntity objects. When a UserEntity is loaded from a model all fields are loaded. For fields referencing foreign entities we use the appropriate foreign model to create the respective entities. For those entities the data will be loaded ondemand. Now your initial reaction might be ...???...!!! let me give you an example a bit of an example:
class UserEntity extends PersistentEntity
{
public function getOrders()
{
$this->getField('orders'); //OrderModel creates OrderEntities with only the ID's set
}
}
class UserModel {
protected $orm;
public function findUsers(IGetOptions $options = null)
{
return $orm->getAllEntities(/*...*/); // Orm creates a list of UserEntities
}
}
class OrderEntity extends PersistentEntity {} // user your imagination
class OrderModel
{
public function findOrdersById(array $ids, IGetOptions $options = null)
{
//...
}
}
In our case $db is an ORM that is able to load entities. The model instructs the ORM to load a set of entities of a specific type. The ORM contains a mapping and uses that to inject all the fields for that entity in to the entity. For foreign fields however only the id's of those objects are loaded. In this case the OrderModel creates OrderEntitys with only the id's of the referenced orders. When PersistentEntity::getField gets called by the OrderEntity the entity instructs it's model to lazy load all the fields into the OrderEntitys. All the OrderEntitys associated with one UserEntity are treated as one result-set and will be loaded at once.
The magic here is that our model and ORM inject all data into the entities and that entities merely provide wrapper functions for the generic getField method supplied by PersistentEntity. To summarize we always load all the fields, but fields referencing a foreign entity are loaded when necessary. Just loading a bunch of fields is not really a performance issue. Load all possible foreign entities however would be a HUGE performance decrease.
Now on to loading a specific set of users, based on a where clause. We provide an object oriented package of classes that allow you to specify simple expression that can be glued together. In the example code I named it GetOptions. It's a wrapper for all possible options for a select query. It contains a collection of where clauses, a group by clause and everything else. Our where clauses are quite complicated but you could obviously make a simpler version easily.
$objOptions->getConditionHolder()->addConditionBind(
new ConditionBind(
new Condition('orderProduct.product', ICondition::OPERATOR_IS, $argObjProduct)
)
);
A simplest version of this system would be to pass the WHERE part of the query as a string directly to the model.
I'm sorry for this quite complicated response. I tried to summarize our framework as quickly and clear as possible. If you have any additional questions feel free to ask them and I'll update my answer.
EDIT: Additionally if you really don't want to load some fields right away you could specify a lazy loading option in your ORM mapping. Because all fields are eventually loaded through the getField method you could load some fields last minute when that method is called. This is not a very big problem in PHP, but I would not recommend for other systems.
These are some different solutions I've seen. There are pros and cons to each of them, but it is for you to decide.
Issue #1: Too many fields
This is an important aspect especially when you take in to account Index-Only Scans. I see two solutions to dealing with this problem. You can update your functions to take in an optional array parameter that would contain a list of a columns to return. If this parameter is empty you'd return all of the columns in the query. This can be a little weird; based off the parameter you could retrieve an object or an array. You could also duplicate all of your functions so that you have two distinct functions that run the same query, but one returns an array of columns and the other returns an object.
public function findColumnsById($id, array $columns = array()){
if (empty($columns)) {
// use *
}
}
public function findById($id) {
$data = $this->findColumnsById($id);
}
Issue #2: Too many methods
I briefly worked with Propel ORM a year ago and this is based off what I can remember from that experience. Propel has the option to generate its class structure based off the existing database schema. It creates two objects for each table. The first object is a long list of access function similar to what you have currently listed; findByAttribute($attribute_value). The next object inherits from this first object. You can update this child object to build in your more complex getter functions.
Another solution would be using __call() to map non defined functions to something actionable. Your __call method would be would be able to parse the findById and findByName into different queries.
public function __call($function, $arguments) {
if (strpos($function, 'findBy') === 0) {
$parameter = substr($function, 6, strlen($function));
// SELECT * FROM $this->table_name WHERE $parameter = $arguments[0]
}
}
I hope this helps at least some what.
Issue #3: Impossible to match an interface
I see the benefit in using interfaces for repositories, so I can swap
out my implementation (for testing purposes or other). My
understanding of interfaces is that they define a contract that an
implementation must follow. This is great until you start adding
additional methods to your repositories like findAllInCountry(). Now I
need to update my interface to also have this method, otherwise, other
implementations may not have it, and that could break my application.
By this feels insane...a case of the tail wagging the dog.
My gut tells me this maybe requires an interface that implements query optimized methods alongside generic methods. Performance sensitive queries should have targeted methods, while infrequent or light-weight queries get handled by a generic handler, maybe the the expense of the controller doing a little more juggling.
The generic methods would allow any query to be implemented, and so would prevent breaking changes during a transition period. The targeted methods allow you to optimize a call when it makes sense to, and it can be applied to multiple service providers.
This approach would be akin to hardware implementations performing specific optimized tasks, while software implementations do the light work or flexible implementation.
I think graphQL is a good candidate in such a case to provide a large scale query language without increasing the complexity of data repositories.
However, there's another solution if you don't want to go for the graphQL for now. By using a DTO where an object is used for carring the data between processes, in this case between the service/controller and the repository.
An elegant answer is already provided above, however I'll try to give another example that I think it's simpler and could serve as a starting point for a new project.
As shown in the code, we would need only 4 methods for CRUD operations. the find method would be used for listing and reading by passing object argument.
Backend services could build the defined query object based on a URL query string or based on specific parameters.
The query object (SomeQueryDto) could also implement specific interface if needed. and is easy to be extended later without adding complexity.
<?php
interface SomeRepositoryInterface
{
public function create(SomeEnitityInterface $entityData): SomeEnitityInterface;
public function update(SomeEnitityInterface $entityData): SomeEnitityInterface;
public function delete(int $id): void;
public function find(SomeEnitityQueryInterface $query): array;
}
class SomeRepository implements SomeRepositoryInterface
{
public function find(SomeQueryDto $query): array
{
$qb = $this->getQueryBuilder();
foreach ($query->getSearchParameters() as $attribute) {
$qb->where($attribute['field'], $attribute['operator'], $attribute['value']);
}
return $qb->get();
}
}
/**
* Provide query data to search for tickets.
*
* #method SomeQueryDto userId(int $id, string $operator = null)
* #method SomeQueryDto categoryId(int $id, string $operator = null)
* #method SomeQueryDto completedAt(string $date, string $operator = null)
*/
class SomeQueryDto
{
/** #var array */
const QUERYABLE_FIELDS = [
'id',
'subject',
'user_id',
'category_id',
'created_at',
];
/** #var array */
const STRING_DB_OPERATORS = [
'eq' => '=', // Equal to
'gt' => '>', // Greater than
'lt' => '<', // Less than
'gte' => '>=', // Greater than or equal to
'lte' => '<=', // Less than or equal to
'ne' => '<>', // Not equal to
'like' => 'like', // Search similar text
'in' => 'in', // one of range of values
];
/**
* #var array
*/
private $searchParameters = [];
const DEFAULT_OPERATOR = 'eq';
/**
* Build this query object out of query string.
* ex: id=gt:10&id=lte:20&category_id=in:1,2,3
*/
public static function buildFromString(string $queryString): SomeQueryDto
{
$query = new self();
parse_str($queryString, $queryFields);
foreach ($queryFields as $field => $operatorAndValue) {
[$operator, $value] = explode(':', $operatorAndValue);
$query->addParameter($field, $operator, $value);
}
return $query;
}
public function addParameter(string $field, string $operator, $value): SomeQueryDto
{
if (!in_array($field, self::QUERYABLE_FIELDS)) {
throw new \Exception("$field is invalid query field.");
}
if (!array_key_exists($operator, self::STRING_DB_OPERATORS)) {
throw new \Exception("$operator is invalid query operator.");
}
if (!is_scalar($value)) {
throw new \Exception("$value is invalid query value.");
}
array_push(
$this->searchParameters,
[
'field' => $field,
'operator' => self::STRING_DB_OPERATORS[$operator],
'value' => $value
]
);
return $this;
}
public function __call($name, $arguments)
{
// camelCase to snake_case
$field = strtolower(preg_replace('/(?<!^)[A-Z]/', '_$0', $name));
if (in_array($field, self::QUERYABLE_FIELDS)) {
return $this->addParameter($field, $arguments[1] ?? self::DEFAULT_OPERATOR, $arguments[0]);
}
}
public function getSearchParameters()
{
return $this->searchParameters;
}
}
Example usage:
$query = new SomeEnitityQuery();
$query->userId(1)->categoryId(2, 'ne')->createdAt('2020-03-03', 'lte');
$entities = $someRepository->find($query);
// Or by passing the HTTP query string
$query = SomeEnitityQuery::buildFromString('created_at=gte:2020-01-01&category_id=in:1,2,3');
$entities = $someRepository->find($query);
I suggest https://packagist.org/packages/prettus/l5-repository as vendor to implement Repositories/Criterias etc ... in Laravel5 :D
I agree with #ryan1234 that you should pass around complete objects within the code and should use generic query methods to get those objects.
Model::where(['attr1' => 'val1'])->get();
For external/endpoint usage I really like the GraphQL method.
POST /api/graphql
{
query: {
Model(attr1: 'val1') {
attr2
attr3
}
}
}
class Criteria {}
class Select {}
class Count {}
class Delete {}
class Update {}
class FieldFilter {}
class InArrayFilter {}
// ...
$crit = new Criteria();
$filter = new FieldFilter();
$filter->set($criteria, $entity, $property, $value);
$select = new Select($criteria);
$count = new Count($criteria);
$count->getRowCount();
$select->fetchOne(); // fetchAll();
So i think
I am trying to improve the method that I am using to to database transactions in a light framework I've built.
Information to understand the question:
Here's a class I've written (where connect.php loads up database credentials; a wrapper for the PHP PDO, stored in $db; and Base.php):
<?php
require_once('connect.php');
class Advertiser extends Base
{
public static function getByID($id)
{
global $db;
$sql = "SELECT * FROM advertiser WHERE advertiserid=?";
$values = array($id);
$res = $db->qwv($sql, $values);
return Advertiser::wrap($res);
}
public static function add($name)
{
$adv = new Advertiser(null, $name);
$res = $adv->save();
return $res;
}
public static function wrap($advs)
{
$advList = array();
foreach( $advs as $adv )
{
array_push($advList, new Advertiser($adv['advertiserid'], $adv['name']));
}
return Advertiser::sendback($advList);
}
private $advertiserid;
private $name;
public function __construct($advertiserid, $name)
{
$this->advertiserid = $advertiserid;
$this->name = $name;
}
public function __get($var)
{
return $this->$var;
}
public function save()
{
global $db;
if( !isset($this->advertiserid) )
{
$sql = "INSERT INTO advertisers (name) VALUES(?)";
$values = array($this->name);
$db->qwv($sql, $values);
if( $db->stat() )
{
$this->advertiserid = $db->last();
return $this;
}
else
{
return false;
}
}
else
{
$sql = "UPDATE advertisers SET name=? WHERE advertiserid=?";
$values = array ($this->name, $this->advertiserid);
$db->qwv($sql, $values);
return $db->stat();
}
}
}
?>
As you can see, it has fairly standard CRUD functions (Edit: Okay, so only CRU, in this implementation). Sometimes, I'll extend a class like this by adding more functions, which is what these classes are intended for. For example, I might add the following function to this class (assuming I add a column isBanned to the database):
public static function getBanned()
{
global $db;
$sql = "SELECT * FROM advertiser WHERE isBanned=1";
$res = $db->q($sql);
return Advertiser::wrap($res);
}
The question:
How can I create a catchall class that will also load up custom model classes when present and necessary?
For example, if I write the following code:
$model = new Catchall();
$banned = $model->Advertiser::getByID(4);
I would expect my catchall class to modify its queries so that all the references to the tables/columns are whatever name I chose (Advertiser, in this case), but in lower case.
In addition, if I wanted to create a custom function like the one I wrote above, I would expect my catchall class to determine that a file exists in its path (previously defined, of course) with the name that I've specified (Advertisers.php, in this case) and load it.
Advertisers.php would extends Catchall and would contain only my custom function.
In this way, I could have a single Catchall class that would work for all CRUD functions, and be able to easily expand arbitrary classes as necessary.
What are the ideas / concepts that I need to understand to do this?
Where can I find examples of this already in the wild, without digging through a lot of CodeIgniter or Zend sourcecode?
What is what I'm trying to do called?
General Stuff: I would look into Doctrine2 for examples of how they make an ORM in PHP. They use mapping in a markup language to say: this table has these columns of this type. Also, while not in PHP, the Django ORM is very easy to use and understand, and working through that tutorial for 20 minutes or so will really open your eyes to some neat possibilities. (it did for me)
A quick search for "php active record lightweight" returned several interesting examples that might start you down the right path.
PHP Ideas: I would look into the magic getter and setter in php, __GET and __SET that will let you set values on your objects without having to make a getter/setter for each field of each table. You could make a single __SET that will make sure that set field is a field in that table, and add it to the list of "fields to update" next time that object is saved. BUT, this is not really a good idea long term, as it gets out of hand quickly, and is brittle.
Advice: Lastly, I worked at a company that used a system that looks almost exactly like this, and I can say unequivocally, you do not want to try to scale this long term. A system like this (the active record pattern) can save massive amounts of time up front, by not having to write queries and things, but can cost tons down the road, if you ever want to start unit testing business logic on the object classes.
For example, it is not possible to mock/dependency inject that static GetById method (it is basically a global method), so every time that is called in code, the code will go to the real database and return a real object. It doesn't take much coding like this to make a system that is almost impossible to test, snarled and tightly coupled to the database.
While they can perform a little slower than your code above, if you are planning on having this around for a considerable amount of time, try looking into ORM tools.
Edit It's called Active Record.
There are a couple different design patterns for what you are trying to do. Look into Data Mapper and Active Record.
Using PHP's "magic method" __get, you can produce this functionality, when you access it via :
$model = new Catchall();
$banned = $model->Advertiser->getByID(4);
... it will a) check to see if the class Advertiser is already defined, b) check for a file called Advertiser.php and include it, or c) return a new instance of a generic class.
The syntax you used in your example with :: assumes that the returned class is static. I have not written this code to contend with that, but it should be trivial to do so.
See the docs: http://www.php.net/manual/en/language.oop5.overloading.php#language.oop5.overloading.methods
Quick and dirty example:
public function __get($name) {
$instance = false;
// see if there is already a class with the requested name
if (class_exists($name)) {
$instance = new $name();
}
// check to see if there is an object def for the requested object
if ($instance === false && file_exists(PATH_TO_OBJECTS.$name.'.php')) {
require_once(PATH_TO_OBJECTS.$name.'.php');
$instance = new $name();
}
// if instace is still not found, load up a generic
if ($instance === false)
$instance = new Catchall($name);
return $instance;
}