Migration problem when database engine is set to MyISAM-CodePudding

I have a database table in my Laravel 8 Project to which I want to assign MyISAM. I do this with this line $table->engine = "MyISAM"; in the migration file. When I start php artisan migrate I get the following error message:

   Illuminate\Database\QueryException 

  SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too
  long; max key length is 1000 bytes (SQL: alter table `view_counters` add index
  `view_counters_countable_type_countable_id_index`(`countable_type`,
  `countable_id`))

Thats my migration file:

        Schema::create('view_counters', function (Blueprint $table) {
            $table->engine = "MyISAM"; 
            $table->id();
            $table->morphs('countable');
            $table->integer('views')->default(0);
        });

I have already read that in this case you can add Schema::defaultStringLength(191) to the boot() method of the AppServiceProvider to avoid this error.

QUESTION: I would like to know what exactly the error message means? Maybe my approach to write the database engine in the migration is wrong. Who knows more?

CodePudding user response：

That error has to do with the string length. By default, laravel's creates string columns with a length of 255 using the charset/collation utf8mb4 (4-byte UTF-8 Unicode Encoding).

Simply lower the default setting in your AppServiceProvider class. (app\Providers\AppServiceProvider.php)

use Illuminate\Support\Facades\Schema;

public function boot()
{
    Schema::defaultStringLength(191); // I think you can use 250 or 249 instead
}

I think you can use 250 (250 * 4 = 1000 <= 1000) or 249 (249 * 4 = 996 < 1000) instead of 191.

The default, 255 (255 * 4 = 1020 > 1000) goes over the limit.

The reason the documentation uses 191 is because InnoDB's index limit is at 767 (191 * 4 = 764 < 767)

More information: 8.x - Migrations - Index Lengths & MySQL / MariaDB