At least 169 people killed in South Sudan 'surprise' attack
For aggregations, things are a little more complex. A full table scan is also required unless the user is grouping by the primary key and sets optimize_aggregation_in_order=1. In this case, a propagation signal is sent once sufficient results are acquired. Provided previous steps of the query are capable of streaming the data, e.g., filter, then this mechanism will work, and the query will terminate early. Normally, however, an aggregation must consume all table data before returning and applying the LIMIT as the final stage.
，详情可参考新收录的资料
Tens of thousands of years ago, as modern humans migrated into northerly territories inhabited by our ancient cousins, the Neanderthals, the two species met – and sometimes mated.，更多细节参见新收录的资料
Борющаяся с раком Симоньян высказалась о проведении прощального вечера18:00。新收录的资料是该领域的重要参考