Memory management is crucial when Laravel applications process massive data. Laravel's LazyCollection provides an efficient solution that loads data on demand rather than loading it all at once. Let's explore this powerful feature to effectively process large datasets.

Understand LazyCollection

LazyCollection is a feature introduced after Laravel 6.0, enabling efficient processing of large data sets by loading projects only when needed. This makes it ideal for handling large files or large database queries without overwhelming the application's memory.

use Illuminate\Support\LazyCollection;

LazyCollection::make(function () {
    $handle = fopen('data.csv', 'r');
    while (($row = fgets($handle)) !== false) {
        yield str_getcsv($row);
    }
})->each(function ($row) {
    // 處理行數(shù)據(jù)
});

LazyCollection Example

Let's look at a practical example, in which we process a large transaction log file and generate a report:

<?php namespace App\Services;

use App\Models\TransactionLog;
use Illuminate\Support\LazyCollection;

class TransactionProcessor
{
    public function processLogs(string $filename)
    {
        return LazyCollection::make(function () use ($filename) {
            $handle = fopen($filename, 'r');

            while (($line = fgets($handle)) !== false) {
                yield json_decode($line, true);
            }
        })
        ->map(function ($log) {
            return [
                'transaction_id' => $log['id'],
                'amount' => $log['amount'],
                'status' => $log['status'],
                'processed_at' => $log['timestamp']
            ];
        })
        ->filter(function ($log) {
            return $log['status'] === 'completed';
        })
        ->chunk(500)
        ->each(function ($chunk) {
            TransactionLog::insert($chunk->all());
        });
    }
}

Using this method, we can:

• Read log files by line
• Convert each log entry to the format we expect
• Filter only completed transactions
• Insert 500 records in batches

For database operations, Laravel provides the cursor() method to create a lazy collection:

<?php namespace App\Http\Controllers;

use App\Models\Transaction;
use Illuminate\Support\Facades\DB;

class ReportController extends Controller
{
    public function generateReport()
    {
        DB::transaction(function () {
            Transaction::cursor()
                ->filter(function ($transaction) {
                    return $transaction->amount > 1000;
                })
                ->each(function ($transaction) {
                    // 處理每筆大額交易
                    $this->processHighValueTransaction($transaction);
                });
        });
    }
}

This implementation ensures efficient memory usage even when processing millions of records, making it ideal for background jobs and data processing tasks.

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