title: KnexJS raw query in migration
body: <p>I have a problem with the following migration in KnexJS, working with PostgreSQL:</p>
  
  <pre><code>exports.up = (knex) =&gt; {
      knex.raw('CREATE EXTENSION IF NOT EXISTS "uuid-ossp"');
  
      return knex.schema.createTable('car_brands', (table) =&gt; {
          table.uuid('brandId').unique().notNullable().primary().defaultTo(knex.raw('uuid_generate_v4()'));
          table.string('name').notNullable().unique();
          table.timestamp('created_at').notNullable().defaultTo(knex.raw('now()'));
          table.timestamp('updated_at').notNullable().defaultTo(knex.raw('now()'));
      });
  };
  
  exports.down = (knex) =&gt; {
      knex.raw('drop extension if exists "uuid-ossp"');
      return knex.schema.dropTable('car_brands');
  };
  </code></pre>
  
  <p>I am using the <code>UUID</code> type for my default values, by using the<br>
  <code>defaultTo(knex.raw('uuid_generate_v4()'))</code>.</p>
  
  <p>However, when running the above migration, by:</p>
  
  <pre><code>knex migrate:latest --env development --knexfile knexfile.js --debug true
  </code></pre>
  
  <p>I get an error that:</p>
  
  <pre><code>function uuid_generate_v4() does not exist
  </code></pre>
  
  <p>Do you know why the <code>knex.raw()</code> query method is not working? </p>