Choose the Right Processing Method: chunk(), lazy(), chunkById(), lazyById()

Understand offset vs keyset pagination when processing large datasets to avoid missing records during updates.

Updating records inside chunk() modifies the result set, causing offset pagination to skip every second chunk. Use chunkById() or lazyById() when updating query columns.

use App\Models\User;

// BAD when updating filtered column: skips records due to offset shift!
User::where('processed', false)->chunk(100, function ($users) {
    $users->each->update(['processed' => true]);
});

// GOOD: Uses primary key comparison (id > last_id) to avoid skipping
User::where('processed', false)->chunkById(100, function ($users) {
    $users->each->update(['processed' => true]);
});

• chunk() uses OFFSET pagination (vulnerable to skipping if queried fields change)
• chunkById() uses keyset pagination (WHERE id > last_id), safe for updates
• lazyById() provides the same keyset safety wrapped in a LazyCollection