I have Question and Answer models. The Question hasMany Answers. Following commands run in the php artisan tinker mode invoke a database query for no apparent reason:
$q = new Question;
$q->answers[] = new Answer; // invokes the below query
// the executed query
select * from `answers` where `answers`.`question_id` is null and `answers`.`question_id` is not null
As you see, there is no need for database call whatsoever. How can I prevent it?
When you do $q->answers, Laravel tries to load all of the answers on the question object - regardless of whether they exist or not.
Any time you access a relationship on a model instance, you can either call it like answers() and get a query builder back, or you can call it like answers without parentheses and Laravel will fetch a collection for you based on the relationship.
You can prevent it easily by doing this:
$q = new Question;
$a = new Answer;
And then, when you're ready to save them, associate them with each other. In its simplest form, that looks like this:
$q->save();
$q->answers()->save($answer);
It's doing that because you're assigning it to the Question object. It wants to see if you're adding an extant record reference. All Laravel Eloquent models contain magic methods for properties, and trying to use them as temporary data storage is a really bad idea unless you've defined a property on them ahead of time for that specific purpose.
Just use a regular array instead and then associate them after the models have been prepared.
Documentation on one-to-many relationships:
https://laravel.com/docs/5.1/eloquent-relationships#one-to-many
Related
[This is to populate data from two tables that one has two foreign keys from the same column as reference on the other table]
https://i.stack.imgur.com/D8fiv.png
[This is my schema for the table with the foreign key]
https://i.stack.imgur.com/eYDL0.png
This is written in laravel and it is working however i have an itchy feeling that this is wrong
As someone else has commented, you should put the code in your question. More context might also be necessary as it's not clear what you are trying to return from your view(). Are you returning $citizen, $family, or both? It would also be helpful to include what version of Laravel you are using. I'll assume you are using the latest Laravel 8.
Your code should work but you are making more work for yourself if you don't utilize Laravel's relationships. If you do, all the query stuff you have in your code can be reduced to just a few short lines of code such as this:
public function view(Citizen $citizen)
{
$citizen->load('family');
return $citizen;
}
Database Migration
You can shorten your migration by using foreignId(). See docs for details
https://laravel.com/docs/8.x/migrations#foreign-key-constraints
Before:
$table->integer('client_id')->unsigned();
$table->foreign('client_id')->references('id')->on('citizens');
After:
$table->foreignId('client_id')->constrained();
Route Model Binding
I'm assuming your view() method is in your controller and is called from a route. Since the one parameter required is the client's id, you can use Route Model Binding and skip fetching the client from the database.
https://laravel.com/docs/8.x/routing#route-model-binding
public function view(Citizen $citizen)
{
// your code
}
Relationships
You seem to have relationships set up but you aren't using them to load data. You should be able to load the related objects without any manual queries.
If you have a belongsTo(One to Many) relationship on the Citizen model to the Family model, you can load it like this:
$citizen->load('family');
or just use it like this
$relationship = $citizen->family->relationship;
I don't know what the relationships between your models are but you should read up on the different relationship types in the docs.
https://laravel.com/docs/8.x/eloquent-relationships
I want to know the difference between laravel eloquent conisgnment->runsheet->name and $consignment->runsheet()->name
i notice that there is performance difference but why? also I notice that when I try to get relationship property like $consignment->runsheet->name it work fine but $consignment->runsheet()->name doesn't work
The first one
$consignment->runsheet
retrieve a collection (so it's already made a query to DB)
while the second
$consignment->runsheet()
is a query builder (hasn't made a database query) you can chain it like any query builder instance
so if you want to get a property from the second one you can do it like:
$consignment->runsheet()->first()->name;
OR
$consignment->runsheet()->value('name');
Im trying to learn GraphQL with Laravel & Lighthouse and have a question Im hoping someone can help me with. I have the following five database tables which are also defined in my Laravel models:
users
books
user_books
book_series
book_copies
I'd like to create a GraphQL endpoint that allows me to get back an array of users and the books they own, where I can pull data from multiple tables into one subfield called "books" like so:
query {
users {
name
books {
title
issue_number
condition
user_notes
}
}
}
To accomplish this in SQL is easy using joins like this:
$users = User::all();
foreach ($users as $user) {
$user['books'] = DB::select('SELECT
book_series.title,
book.issue_number
book_copies.condition,
user_books.notes as user_notes
FROM user_books
JOIN book_copies ON user_books.book_copy_id = book_copies.id
JOIN books ON book_copies.book_id = books.id
JOIN book_series ON books.series_id = book_series.id
WHERE user_books.user_id = ?',[$user['id']])->get();
}
How would I model this in my GraphQL schema file when the object type for "books" is a mashup of properties from four other object types (Book, UserBook, BookCopy, and BookSeries)?
Edit: I was able to get all the data I need by doing a query that looks like this:
users {
name
userBooks {
user_notes
bookCopy {
condition
book {
issue_number
series {
title
}
}
}
}
}
However, as you can see, the data is separated into multiple child objects and is not as ideal as getting it all in one flat "books" object. If anyone knows how I might accomplish getting all the data back in one flat object, Id love to know.
I also noticed that the field names for the relationships need to match up exactly with my controller method names within each model, which are camelCase as per Laravel naming conventions. Except for my other fields are matching the database column names which are lower_underscore. This is a slight nitpick.
Ok, after you edited your question, I will write the answer here, to answer your new questions.
However, as you can see, the data is separated into multiple child objects and is not as ideal as getting it all in one flat "books" object. If anyone knows how I might accomplish getting all the data back in one flat object, Id love to know.
The thing is, that this kind of fetching data is a central idea of GraphQL. You have some types, and these types may have some relations to each other. So you are able to fetch any relations of object, in any depth, even circular.
Lighthouse gives you out of the box support to eloquent relations with batch loading, avoiding the N+1 performance problem.
You also have to keep in mind - every field (literally, EVERY field) in your GraphQL definition is resolved on server. So there is a resolve function for each of the fields. So you are free to write your own resolver for particular fields.
You actually can define a type in your GraphQL, that fits your initial expectation. Then you can define a root Query field e.g. fetchUsers, and create you custom field resolver. You can read in the docs, how it works and how to implement this: https://lighthouse-php.com/5.2/the-basics/fields.html#hello-world
In this field resolver you are able to make your own data fetching, even without using any Laravel/Eloquent API. One thing you have to take care of - return a correct data type with the same structure as your return type in GraphQL for this field.
So to sum up - you have the option to do this. But in my opinion, you have to write more own code, cover it with tests on you own, which turns out in more work for you. I think it is simpler to use build-in directives, like #find, #paginate, #all in combination with relations-directives, which all covered with tests, and don't care about implementation.
I also noticed that the field names for the relationships need to match up exactly with my controller method names within each model, which are camelCase as per Laravel naming conventions.
You probably means methods within Model class, not controller.
Lighthouse provides a #rename directive, which you can use to define different name in GraphQL for your attributes. For the relation directives you can pass an relation parameter, which will be used to fetch the data. so for your example you can use something like this:
type User {
#...
user_books: [Book!]! #hasMany(relation: "userBooks")
}
But in our project we decided to use snak_case also for relations, to keep GraphQL clean with consistent naming convention and less effort
Back when I was using CodeIgniter I had functions in my models like
public function GetArticlesFormatted($inactive = FALSE)
and then in my controller I could have had
$articles->GetArticlesFormatted(true);
And so on.
How should I achieve the same with Laravel 5.4? The database of the app I'm building is already built and full and is a mess so most of the "automated" super-restrictive things that Laravel has don't work out of the box.
For example there is a Country Code that I'm retrieving and I need it as is, but in some instances I need it converted in a Country Name which I had in another table.
Right now I just have in my controller wherever I am retrieving data from the model:
$countryResult = Country::where('country_code', $item['country_code'])->first();
$countryArray = $countryResult->toArray();
$item['country'] = $countryArray['country_name'];
Can I somehow achieve that in a more elegant way?
I tried accessors but for some reason couldn't get anything to work for my purposes.
A select query can be used to limit selection to a particular column.
$countryName = Country::select('country_name')
->where('country_code', $item['country_code'])
->first();
I have defined a many-to-many relationship between Student and Seminar models. How can I find out if one particular student is attending one particular seminar? Non-working example of what I want to achieve is illustrated below:
$seminar->students()->contains($student->id);
The following error is shown when using the above code snippet:
BadMethodCallException with message 'Call to undefined method Illuminate\Database\Query\Builder::contain()'
Try instead:
$seminar->students->contains($student->id);
Presuming $student contains an instance of the Student model you can simplify it further and just use:
$seminar->students->contains($student);
When you add parentheses you're using the Laravel query builder, and you never completed the query. To do it in the manner you had originally you would need:
$seminar->students()->get()->contains($student->id);
This method could be useful if you wanted to add constraints when fetching your students.
But generally you can omit the parentheses and a Collection will be returned, allowing you to use methods like contains.
This has the additional benefit of not re-querying the database once the relationship is loaded, so will generally be a far more efficient means of fetching relationships.
If you haven't already loaded the students and want a database efficient method of checking you could instead use:
$seminar->students()->where('students.id', $student->id)->exists();
In your case the exception is you are calling 'contains()' function (which is for Laravel Collection) on 'Query Builder'. It should be
$seminar->students->get()->contains($student->id);
but this is inefficient since this will retrieve all the students of the seminar.
so instead,
$seminar->students()->wherePivot('student_id', $student->id)->exists();
this method will check in the intermediate table of many to many relationship for particular seminar-student pair, and will return whether exists or not.
The accepted answer is wrong. $seminar->students()->exists($student->id) does not check if the relationship exists. It only checks if the student exists. The student could belong to any seminar and it would still return true.
The correct way to check if a relationship exists without fetching records from the database would be:
$seminar->students()->whereId($student->id)->exists()
Check using query
$seminar->students()->whereKey($student->getKey())->exists();
Check after query (angry), can have memory problems if you have multiple attachments
$seminar->students->contains($student->getKey());
// or
$seminar->students()->get()->contains($student->getKey());