/**
 * Enable the update.module by default on sites that upgrade.
 *
 * This cannot just rely on update.install to install the schema. If,
 * in the future, someone decides to change the schema for the
 * {cache_update} table, this update would cause uncertainty in the
 * state of the DB, since the effect of running this update would
 * change. For example, if the schema is changed in update #6101, and
 * a site upgrades direct from 5.x to 6.1, update #6026 would create
 * the table with the new schema, and then update #6101 would fail,
 * since it's trying to alter the old schema into the new
 * schema. Therefore, we must hard-code the particular version of the
 * schema we mean during update #6026, and then future upgrades that
 * might attempt to modify the schema of this table will be starting
 * from a known state. See http://drupal.org/node/150220 for more.
 */
function system_update_6026() {
  $ret = array();
  $schema['cache_update'] = array(
    'fields' => array(
      'cid'        => array('type' => 'varchar', 'length' => 255, 'not null' => TRUE, 'default' => ''),
      'data'       => array('type' => 'blob', 'not null' => FALSE, 'size' => 'big'),
      'expire'     => array('type' => 'int', 'not null' => TRUE, 'default' => 0),
      'created'    => array('type' => 'int', 'not null' => TRUE, 'default' => 0),
      'headers'    => array('type' => 'text', 'not null' => FALSE),
      'serialized' => array('type' => 'int', 'size' => 'small', 'not null' => TRUE, 'default' => 0)
    ),
    'indexes' => array('expire' => array('expire')),
    'primary key' => array('cid'),
  );
  db_create_table($ret, 'cache_update', $schema['cache_update']);
  drupal_set_installed_schema_version('update', 0);
  module_enable(array('update'));
  menu_rebuild();
  return $ret;
}