interface QueryAggregateInterface

interface QueryAggregateInterface extends QueryInterface {
    
    /**
     * Specifies a field and a function to aggregate on.
     *
     * Available functions: SUM, AVG, MIN, MAX and COUNT.
     *
     * @todo What about GROUP_CONCAT support?
     *
     * @param string $field
     *   The name of the field to aggregate by.
     * @param string $function
     *   The aggregation function, for example COUNT or MIN.
     * @param string $langcode
     *   (optional) The language code.
     * @param string $alias
     *   (optional) The key that will be used on the resultset.
     *
     * @return $this
     *   The called object.
     */
    public function aggregate($field, $function, $langcode = NULL, &$alias = NULL);
    
    /**
     * Specifies the field to group on.
     *
     * @param string $field
     *   The name of the field to group by.
     *
     * @return $this
     *   The called object.
     */
    public function groupBy($field);
    
    /**
     * Sets a condition for an aggregated value.
     *
     * @param string $field
     *   The name of the field to aggregate by.
     * @param string $function
     *   The aggregation function, for example COUNT or MIN.
     * @param mixed $value
     *   The actual value of the field.
     * @param $operator
     *   Possible values:
     *   - '=', '<>', '>', '>=', '<', '<=', 'STARTS_WITH', 'CONTAINS',
     *     'ENDS_WITH': These operators expect $value to be a literal of the
     *     same type as the column.
     *   - 'IN', 'NOT IN': These operators expect $value to be an array of
     *     literals of the same type as the column.
     *   - 'BETWEEN', 'NOT BETWEEN': These operators expect $value to be an array
     *     of two literals of the same type as the column.
     * @param string $langcode
     *   (optional) The language code.
     *
     * @return $this
     *   The called object.
     *
     * @see \Drupal\Core\Entity\Query\QueryInterface::condition()
     */
    public function conditionAggregate($field, $function = NULL, $value = NULL, $operator = '=', $langcode = NULL);
    
    /**
     * Queries for the existence of a field.
     *
     * @param string $field
     *   The name of the field.
     * @param string $function
     *   The aggregate function.
     * @param $langcode
     *   (optional) The language code.
     *
     * @return $this
     *   The called object.
     */
    public function existsAggregate($field, $function, $langcode = NULL);
    
    /**
     * Queries for the nonexistence of a field.
     *
     * @param string $field
     *   The name of a field.
     * @param string $function
     *   The aggregate function.
     * @param string $langcode
     *   (optional) The language code.
     *
     * @return $this
     *   The called object.
     */
    public function notExistsAggregate($field, $function, $langcode = NULL);
    
    /**
     * Creates an object holding a group of conditions.
     *
     * See andConditionAggregateGroup() and orConditionAggregateGroup() for more.
     *
     * @param string $conjunction
     *   - AND (default): this is the equivalent of andConditionAggregateGroup().
     *   - OR: this is the equivalent of andConditionAggregateGroup().
     *
     * @return ConditionInterface
     *   An object holding a group of conditions.
     */
    public function conditionAggregateGroupFactory($conjunction = 'AND');
    
    /**
     * Sorts by an aggregated value.
     *
     * @param string $field
     *   The name of a field.
     * @param string $function
     *   The aggregate function. This is only marked optional for interface
     *   compatibility, it is illegal to leave it out.
     * @param string $direction
     *   The order of sorting, either DESC for descending of ASC for ascending.
     * @param string $langcode
     *   (optional) The language code.
     *
     * @return $this
     *   The called object.
     */
    public function sortAggregate($field, $function, $direction = 'ASC', $langcode = NULL);
    
    /**
     * Executes the aggregate query.
     *
     * @return array
     *   A list of result row arrays. Each result row contains the aggregate
     *   results as keys and also the groupBy columns as keys:
     *
     *   @code
     *     $result = $query
     *       ->aggregate('nid', 'count')
     *       ->condition('status', 1)
     *       ->groupby('type')
     *       ->execute();
     *   @endcode
     *   Will return:
     *   @code
     *     $result[0] = array('count_nid' => 3, 'type' => 'page');
     *     $result[1] = array('count_nid' => 4, 'type' => 'article');
     *   @endcode
     */
    public function execute();

}