Error: Specified key length exceeds maximum limit during migration

[HMAHD]

Bug Description:

When attempting to create a migration for the personal_access_tokens table in Laravel, a "Specified key was too long" error occurs. This error arises because Laravel tries to create an index with a key length that exceeds the maximum allowed by the database engine (MySQL), causing the migration to fail.

Fixed Code:

The issue can be resolved by adjusting the migration code to specify a custom index name with a shorter key length for the tokenable_type column. Additionally, we explicitly define the tokenable_type as a string with the desired length and tokenable_id as an unsigned big integer. After defining the columns, we add the index separately to ensure it's created with the correct length.

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

class CreatePersonalAccessTokensTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('personal_access_tokens', function (Blueprint $table) {
            $table->id();
            
            // Use a smaller index key length
            $table->string('tokenable_type', 191); // Adjust the length as needed
            $table->unsignedBigInteger('tokenable_id');
            
            $table->string('name');
            $table->string('token', 64)->unique();
            $table->text('abilities')->nullable();
            $table->timestamp('last_used_at')->nullable();
            $table->timestamps();

            // Add an index separately
            $table->index(['tokenable_type', 'tokenable_id']);
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('personal_access_tokens');
    }

}

[opariltay]

Hey @HMAHD ,

Thanks for raising that issue. According to official Laravel documentation, this happens when you are running a version of MySQL older than the 5.7.7 release or MariaDB older than the 10.2.2 release.

Please see below pages for detailed explanation:
https://laravel.com/docs/8.x/migrations#index-lengths-mysql-mariadb
https://stackoverflow.com/a/42245921

Anyone with an older MySQL or MariaDB release can refer to this issue in the future.

Thanks.