Laravel migration [ErrorException]未定义索引:index_type

我正在尝试迁移我的laravel项目。

但是当我输入迁移命令时，我得到这个错误。我不明白为什么它给我这个错误，当我试图迁移我的项目。

[ErrorException]             
  Undefined index: index_type  

Exception trace:
 () at /var/www/vendor/doctrine/dbal/lib/Doctrine/DBAL/Schema/MySqlSchemaManager.php:75
 Illuminate'Foundation'Bootstrap'HandleExceptions->handleError() at /var/www/vendor/doctrine/dbal/lib/Doctrine/DBAL/Schema/MySqlSchemaManager.php:75
 Doctrine'DBAL'Schema'MySqlSchemaManager->_getPortableTableIndexesList() at /var/www/vendor/doctrine/dbal/lib/Doctrine/DBAL/Schema/AbstractSchemaManager.php:193
 Doctrine'DBAL'Schema'AbstractSchemaManager->listTableIndexes() at /var/www/vendor/doctrine/dbal/lib/Doctrine/DBAL/Schema/AbstractSchemaManager.php:286
 Doctrine'DBAL'Schema'AbstractSchemaManager->listTableDetails() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Schema/Grammars/Grammar.php:320
 Illuminate'Database'Schema'Grammars'Grammar->getChangedDiff() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Schema/Grammars/Grammar.php:302
 Illuminate'Database'Schema'Grammars'Grammar->compileChange() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Schema/Blueprint.php:107
 Illuminate'Database'Schema'Blueprint->toSql() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Schema/Blueprint.php:82
 Illuminate'Database'Schema'Blueprint->build() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Schema/Builder.php:229
 Illuminate'Database'Schema'Builder->build() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Schema/Builder.php:130
 Illuminate'Database'Schema'Builder->table() at /var/www/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:237
 Illuminate'Support'Facades'Facade::__callStatic() at /var/www/database/migrations/2016_10_25_222438_update_relationships_for_employee.php:20
 Illuminate'Support'Facades'Schema::table() at /var/www/database/migrations/2016_10_25_222438_update_relationships_for_employee.php:20
 UpdateRelationshipsForEmployee->up() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Migrations/Migrator.php:373
 Illuminate'Database'Migrations'Migrator->Illuminate'Database'Migrations'{closure}() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Migrations/Migrator.php:380
 Illuminate'Database'Migrations'Migrator->runMigration() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Migrations/Migrator.php:162
 Illuminate'Database'Migrations'Migrator->runUp() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Migrations/Migrator.php:130
 Illuminate'Database'Migrations'Migrator->runMigrationList() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Migrations/Migrator.php:97
 Illuminate'Database'Migrations'Migrator->run() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Console/Migrations/MigrateCommand.php:66
 Illuminate'Database'Console'Migrations'MigrateCommand->fire() at n/a:n/a
 call_user_func_array() at /var/www/vendor/laravel/framework/src/Illuminate/Container/Container.php:508
 Illuminate'Container'Container->call() at /var/www/vendor/laravel/framework/src/Illuminate/Console/Command.php:169
 Illuminate'Console'Command->execute() at /var/www/vendor/symfony/console/Command/Command.php:256
 Symfony'Component'Console'Command'Command->run() at /var/www/vendor/laravel/framework/src/Illuminate/Console/Command.php:155
 Illuminate'Console'Command->run() at /var/www/vendor/laravel/framework/src/Illuminate/Console/Command.php:185
 Illuminate'Console'Command->call() at /var/www/vendor/laravel/framework/src/Illuminate/Database/Console/Migrations/RefreshCommand.php:66
 Illuminate'Database'Console'Migrations'RefreshCommand->fire() at n/a:n/a
 call_user_func_array() at /var/www/vendor/laravel/framework/src/Illuminate/Container/Container.php:508
 Illuminate'Container'Container->call() at /var/www/vendor/laravel/framework/src/Illuminate/Console/Command.php:169
 Illuminate'Console'Command->execute() at /var/www/vendor/symfony/console/Command/Command.php:256
 Symfony'Component'Console'Command'Command->run() at /var/www/vendor/laravel/framework/src/Illuminate/Console/Command.php:155
 Illuminate'Console'Command->run() at /var/www/vendor/symfony/console/Application.php:820
 Symfony'Component'Console'Application->doRunCommand() at /var/www/vendor/symfony/console/Application.php:187
 Symfony'Component'Console'Application->doRun() at /var/www/vendor/symfony/console/Application.php:118
 Symfony'Component'Console'Application->run() at /var/www/vendor/laravel/framework/src/Illuminate/Foundation/Console/Kernel.php:121
 Illuminate'Foundation'Console'Kernel->handle() at /var/www/artisan:36

我的迁移文件在下面

<?php
use Illuminate'Support'Facades'Schema;
use Illuminate'Database'Schema'Blueprint;
use Illuminate'Database'Migrations'Migration;
class UpdateRelationshipsForEmployee extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        //
        Schema::table('employee',function ($table){
            $table->integer('retail_id')->unsigned()->index()->change();
        });
    }
    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::table('employee', function ($table){
            $table->integer('retail_id')->change();
        });
        //
    }
}