# Chunk reading

Importing a large file can have a huge impact on the memory usage, as the library will try to load the entire sheet into memory.

To mitigate this increase in memory usage, you can use the WithChunkReading concern. This will read the spreadsheet in chunks and keep the memory usage under control.

namespace App\Imports;

use App\User;
use Maatwebsite\Excel\Concerns\ToModel;
use Maatwebsite\Excel\Concerns\WithChunkReading;

class UsersImport implements ToModel, WithChunkReading
{
    public function model(array $row)
    {
        return new User([
            'name' => $row[0],
        ]);
    }
    
    public function chunkSize(): int
    {
        return 1000;
    }
}
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A chunk size of 1000 will not be the most optimal situation for your import. Play around with this number to find the sweet spot.

# Using it together with Batch Inserts

The most ideal situation (regarding time and memory consumption) you will find when combining batch inserts and chunk reading.

namespace App\Imports;

use App\User;
use Maatwebsite\Excel\Concerns\ToModel;
use Maatwebsite\Excel\Concerns\WithBatchInserts;
use Maatwebsite\Excel\Concerns\WithChunkReading;

class UsersImport implements ToModel, WithBatchInserts, WithChunkReading
{
    public function model(array $row)
    {
        return new User([
            'name' => $row[0],
        ]);
    }
    
    public function batchSize(): int
    {
        return 1000;
    }
    
    public function chunkSize(): int
    {
        return 1000;
    }
}
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# Keep Track of the Row number

If you need the row number you can use the RemembersRowNumber Trait.

namespace App\Imports;

use App\User;
use Maatwebsite\Excel\Concerns\ToModel;
use Maatwebsite\Excel\Concerns\RemembersRowNumber;
use Maatwebsite\Excel\Concerns\WithChunkReading;

class UsersImport implements ToModel, WithChunkReading
{
    use RemembersRowNumber;

    public function model(array $row)
    {
        $currentRowNumber = $this->getRowNumber();

        return new User([
            'name' => $row[0],
        ]);
    }
    
    public function chunkSize(): int
    {
        return 1000;
    }
}
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Remembering row numbers is only intender for ToModel imports.

If you only need the information about the offset of the chunk you can use the RemembersChunkOffset Trait.

namespace App\Imports;

use App\User;
use Maatwebsite\Excel\Concerns\ToModel;
use Maatwebsite\Excel\Concerns\RemembersChunkOffset;
use Maatwebsite\Excel\Concerns\WithChunkReading;

class UsersImport implements ToModel, WithChunkReading
{
    use RemembersChunkOffset;

    public function model(array $row)
    {
        $chunkOffset = $this->getChunkOffset();

        return new User([
            'name' => $row[0],
        ]);
    }
    
    public function chunkSize(): int
    {
        return 1000;
    }
}
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