gistfile1.php

/**
 * Implements hook_facetapi_facet_info().
 * Provides the definitions for the extra facets.
 *
 * @param array $searcher_info
 *   The definition of the searcher that facets are being collected for.
 *
 * @return array
 *   An associative array keyed by unique name of the facet.
 */
function apachesolr_external_index_facetapi_facet_info($searcher_info) {
  $facets = array();
  $searcher_info = facetapi_get_searcher_info();

  $facets['cat'] = array(
    'name' => 'category',
    'label' => t('Category'),
    'description' => t('Filter by category.'),
    'field' => 'ss_cat',
    'field alias' => 'cat',
    'field api bundles' => array('node'),
    'facet mincount allowed' => TRUE,
    'dependency plugins' => array('bundle', 'role'),
  );

   return $facets;
}