Laravel lazy loading vs eager loading
Lazy loading only queries when accessing associations can easily lead to N 1 problems, which is suitable for scenarios where the associated data is not determined. 2. Emergency loading uses with() to load associated data in advance to avoid N 1 queries, which is suitable for batch processing scenarios; 3. Emergency loading should be used to optimize performance, and N 1 problems can be detected through tools such as Laravel Debugbar, and the $with attribute of the model is carefully used to avoid unnecessary performance overhead.
In Laravel, Lazy Loading and Eager Loading are the two main ways to process model-associated data. They are clearly different in performance and usage scenarios, and understanding their differences is very important for optimizing application performance.
What is Lazy Loading
Lazy loading refers to the database that only when accessing the model's association relationship, it will query and load data.
for example:
$books = Book::all();
foreach ($books as $book) {
echo $book->author->name; // Every time you access author, a query will be triggered} The above code will first query all books (1 query), and then each time you access author of a book , you will execute a query separately to obtain the author information. If there are 100 books, an additional 100 queries will be performed - this is a typical N 1 query problem .
✅ Pros:
- Simple to use, intuitive code
- Load data only when it is really needed
❌ Disadvantages:
- It can easily lead to N 1 query problems and seriously reduce performance
- Especially dangerous when accessing associated data in loops
What is emergency loading
Emergency loading is to load the associated data in advance when querying the main model, using the with() method.
for example:
$books = Book::with('author')->get();
foreach ($books as $book) {
echo $book->author->name; // The data has been loaded, and the database is no longer query}This code will only execute 2 queries:
- Query all books
- Query all authors corresponding to these books (by
INquery)
✅ Pros:
- Avoid N 1 problems and greatly improve performance
- Suitable for batch processing of associated data
❌ Disadvantages:
- If the associated data is large but not actually used, it will cause waste of resources
- Not available for dynamic conditions (unless constraints are used)
How to choose: lazy load vs urgent load?
| Scene | Recommended method | illustrate |
|---|---|---|
| Accessing associated data in loop | ✅ Emergency loading | Avoid N 1 query |
| Process only a small amount of data or not sure if association is required | ✅ Lazy loading | Simple and direct, avoid unnecessary inquiries |
| Complex or large data volume | ⚠️ Cautioned to load urgently | May cause high memory usage |
| Need to add conditions to the association | ✅ with() closure | Support conditional filtering |
Example: Emergency loading with conditions
$books = Book::with(['author' => function ($query) {
$query->where('active', 1);
}])->get();How to detect N 1 problems?
You can use Laravel's debugging tools, such as:
- Laravel Debugbar
- Clockwork
- Or use
DB::listen()to listen to the number of queries
These tools can help you discover unexpected multiple queries.
Best Practice Recommendations
- Emergency loading is preferred by default , especially when the list page or API returns multiple resources
- Preload common associations using
with() - Avoid accessing unpreloaded associations in Blade templates (easily trigger lazy loading)
- Some associations can be automatically preloaded (used with caution) by setting
$withproperty through the model:
class Book extends Model
{
protected $with = ['author']; // Automatic preload author
} ⚠️ Note: Global $with affects all queries and may result in unnecessary performance overhead.
Basically that's it. Simply put: lazy loading is convenient but easy to get stuck, urgent loading is efficient but planning is necessary . In actual development, N 1 queries should be avoided as much as possible, and with() should be used first to optimize performance.
The above is the detailed content of Laravel lazy loading vs eager loading. For more information, please follow other related articles on the PHP Chinese website!
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