(PECL sphinx >= 0.1.0)
SphinxClient::setGroupDistinct — Set attribute name for per-group distinct values count calculations
Sets attribute name for per-group distinct values count calculations. Only available for grouping queries. For each group, all values of attribute will be stored, then the amount of distinct values will be calculated and returned to the client. This feature is similar to COUNT(DISTINCT) clause in SQL.
A string containing group-by attribute name.
如果成功则返回 TRUE，失败则返回 FALSE。