It seems that eloquent uses a single query for "with" regardless of how many ids there are
Book::with('author')->get();
This would trigger those two queries:
SELECT * FROM books;
SELECT * FROM authors WHERE id IN (...);
The second query may have thousands of author ids in the where clause which might cause problems with performance.
Is there some way so it would chunk that when using with?
I am aware that it is generally not a good idea to query such big result sets.
Yes there are, and its clear in the documentation, you can do something like this:
use App\Models\Flight;
Flight::chunk(200, function ($flights) {
foreach ($flights as $flight) {
//
}
});
Or you can also do this:
use App\Models\Flight;
foreach (Flight::lazy() as $flight) {
//
}
You can get the details in the documentation to learn more:
https://laravel.com/docs/9.x/eloquent#chunking-results
if you need only Books and count authors you can use withCount method
Book::withCount('author')->get();
Related
One of my models contains the following:
public function from()
{
return $this->belongsTo(Station::class, 'from_station_id');
}
public function to()
{
return $this->belongsTo(Station::class, 'to_station_id');
}
In order to use this I'm using the with('to', 'from') method. Which results in the following:
select * from "stations" where "stations"."id" in ('1')
select * from "stations" where "stations"."id" in ('2')
Two cached queries one for "to's" and one for "from's". At the moment with 1 record they are "useful". But in the future they will have a lot of duplicate IDs..
Does Laravel offer an option to combine these?
Assuming you'll need to access them from the model by the relation, like $model->from->first() or $model->to->count(), your best option would be to stick with 2 queries. A query with where in clause is not that heavy and you can additionally cache them to speed up.
In Laravel 4.2 I have a model called Product with many-to-many relationshis to other models like Country or Category. I want to filter out products that are "incomplete", which means they have no connected countries or no connected categories. I can use whereDoesntHave() method to filter out one relation. When I use it two times in one query it creates AND condition, but I need OR. I can't find orWhereDoesntHave() method in API documentation. I can't pass multiple relations as arguments because it expects first argument to be a string.
I need something like this:
$products = Product::whereDoesntHave('categories')->orWhereDoesntHave('countries')->get();
Is there any way to achive whereDoesntHave() with multiple OR conditions?
You can use doesntHave and specify the boolean operator:
$products = Product::doesntHave('categories')->doesntHave('countries', 'or')->get();
Actually you only need whereDoesntHave if you want to pass in a closure to filter the related models before checking if any of them exist. In case you want to do that you can pass the closure as third argument:
$products = Product::doesntHave('categories', 'or', function($q){
$q->where('active', false);
})->doesntHave('countries', 'or')->get();
Since Laravel 5.5 there is an orWhereDoesntHave function.
You may use it like this
Product::whereDoesntHave('categories', function($q){ //... })
->orWhereDoesntHave('countries', function($q){//...})
->get();
From you example it seems that you are not using a where clause, so you may just use
Product::doesntHave('categories')
->orDoesntHave('countries')
->get();
Use
Product::whereDoesntHave('categories')->doesntHave('countries', 'or')->get();
Laravel Source Code:
whereDoesntHave https://github.com/illuminate/database/blob/master/Eloquent/Builder.php#L654
calls
https://github.com/illuminate/database/blob/master/Eloquent/Builder.php#L628
internally.
Let’s say we have Authors and Books, with 1-n relationship – one Author can have one or many Books. Here’s how it looks in app\Author.php:
public function books()
{
return $this->hasMany(\App\Book::class, 'author_id');
}
Now, what if we want to show only those Authors that have at least one book? Simple, there’s method has():
$authors = Author::has('books')->get();
Similarly, there’s an opposite method – what if we want to query only the authors without any books? Use doesnthave():
$authors = Author::doesnthave('books')->get();
It’s not only convenient, but also super-easy to read and understand, even if you’re not a Laravel developer, right?
I'm working in Laravel 4, and I have a Child model with multiple EducationProfiles:
class Child extends EloquentVersioned
{
public function educationProfiles()
{
return $this->hasMany('EducationProfile');
}
}
If I wanted to get all the EducationProfiles for each kid under age 10 it would be easy:
Child::where('date_of_birth','>','2004-03-27')->with('educationProfiles')->all();
But say (as I do) that I would like to use with() to grab a calculated value for the Education Profiles of each of those kids, something like:
SELECT `education_profiles`.`child_id`, GROUP_CONCAT(`education_profiles`.`district`) as `district_list`
In theory with() only works with relationships, so do I have any options for associating the district_list fields to my Child models?
EDIT: Actually, I was wondering whether with('educationProfiles') generates SQL equivalent to:
EducationProfile::whereIn('id',array(1,2,3,4))
or whether it's actually equivalent to
DB::table('education_profiles')->whereIn('id',array(1,2,3,4))
The reason I ask is that in the former I'm getting models, if it's the latter I'm getting unmodeled data, and thus I can probably mess it up as much as I want. I assume with() generates an additional set models, though. Anybody care to correct or confirm?
Ok, I think I've cracked this nut. No, it is NOT possible to eager load arbitrary queries. However, the tools have been provided by the Fluent query builder to make it relatively easy to replicate eager loading manually.
First, we leverage the original query:
$query = Child::where('date_of_birth','>','2004-03-27')->with('educationProfiles');
$children = $query->get();
$eagerIds = $query->lists('id');
Next, use the $eagerIds to filterDB::table('education_profile') in the same way that with('educationProfiles') would filter EducationProfile::...
$query2 = DB::table('education_profile')->whereIn('child_id',$eagerIds)->select('child_id', 'GROUP_CONCAT(`education_profiles`.`district`) as `district_list`')->groupBy('child_id');
$educationProfiles = $query2->lists('district_list','child_id');
Now we can iterate through $children and just look up the $educationProfiles[$children->id] values for each entry.
Ok, yes, it's an obvious construction, but I haven't seen it laid out explicitly anywhere before as a means of eager loading arbitrary calculations.
You can add a where clause to your hasMany() call like this:
public function educationProfilesUnderTen() {
$ten_years_ago = (new DateTime('10 years ago'))->format('Y-m-d');
return $this->hasMany('EducationProfile')->where('date_of_birth', '>', $ten_years_ago)
}
In Symfony 2 book there is an example of how to do that for ONE $product: http://symfony.com/doc/2.0/book/doctrine.html#fetching-related-objects
It is quite simple:
public function showAction($id)
{
$product = $this->getDoctrine()
->getRepository('AcmeStoreBundle:Product')
->find($id);
$categoryName = $product->getCategory()->getName();
// ...
}
But what if i want to fetch ALL products with category info joined automatically to each project?
Thank you!
This will do the trick:
$products = $this->getDoctrine()->getRepository('AcmeStoreBundle:Product')->findAll();
However, each time you do a getCategory on a product a sql query will be triggered which could result in performance issues.
What you really want to do is to make yourself a ProductManager service and write an explicit query joining product and category. So only one sql query will be generated. The Doctrine 2 manual has plenty of examples.
http://docs.doctrine-project.org/projects/doctrine-orm/en/2.1/reference/query-builder.html
You can either iterate over the products and get the categories from there. Adjusting the fetch mode on the relations might help in reducing the amount of queries performed.
However, you might also just write a custom DQL query to get what you need. It might look like something like this:
SELECT p, c
FROM AcmeStoreBundle:Product p
INNER JOIN p.category c
Seems like such a simple thing, but I can't get my query to return the number of records in a group. Here's my statement:
public function getGroupCount($user_id)
{
$q = Doctrine_Query::create()
->select('ss.*')
->from('SalarySurvey ss')
->where('ss.user_id=?', $user_id)
->groupBy('created_at')
->execute();
return $q->rowCount();
}
rowCount() does not work in the above query.
It might also be helpful to know that this is being used in a foreach statement.
As CappY suggested, this is not possible in Doctrine 1.2, as far as I know. As a work-around, I was able to finally get a count for each grouping by adding another field to the table and setting that field the same for each group at save time. Then I changed my query to pull that field and just did a simple:
$q->count();
Never work with Doctrine 1.2, but can't U use php's count function or SELECT COUNT() AS 'cnt' ?
return count($q);