Laravel: "Unknown database type _int4 requested" in migration
<p>I has created column <code>user_id</code> in one migration:</p>

<pre><code>public function up()
{
    Schema::create($this-&gt;_tableName, function (Blueprint $table) {
        $table-&gt;increments('id');

        $table-&gt;unsignedInteger('user_id')-&gt;index();
        $table-&gt;foreign('user_id')-&gt;references('id')-&gt;on('users')-&gt;onDelete('cascade');
        ...
</code></pre>

<p>Now I try to make this column as nullable in second migration:</p>

<pre><code>public function up()
{
    Schema::table($this-&gt;_tableName, function(Blueprint $table) {
        $table-&gt;unsignedInteger('user_id')-&gt;nullable()-&gt;change();
    });
}
</code></pre>

<p>But I obtain next message:</p>

<pre><code>$ php artisan migrate


  [Doctrine\DBAL\DBALException]                                                                          
  Unknown database type _int4 requested, Doctrine\DBAL\Platforms\PostgreSqlPlatform may not support it.  
</code></pre>

<p>What is wrong?</p>