public function facet($field, $min = 0, $multi = false, $postCollapsing = false) {
		if(empty($this->data['facets'])) {
			$this->data['facets'] = array();
		}
		$this->data['facets'][] = array(
			'field' => $field,
			'minCount' => $min,
			'multivalued' => $multi,
			'postCollapsing' => $postCollapsing
		);
		return $this;
	}