通用的优化手段是EXPLAIN ANALYZE/PERFORMANCE命令查看执行过程的瓶颈算子,然后进行针对性优化。 基表扫描时,对于点查或者范围扫描等过滤大量数据的查询,如果使用SeqScan全表扫描会比较耗时,可以在条件列上建立索引选择IndexScan进行索引扫描提升扫描效率。如下示例: 上述例子中,全表扫描返回3360条数据,过滤掉大量数据,在sss...
内存使用自动扩展次数(auto spread times) 是否提前下盘(early spilled),及下盘信息,包括重复下盘次数(spill Time(s)),内外表下盘分区数(inner/outer partition spill num),下盘文件数(temp file num),下盘数据量及最小和最大分区的下盘数据量(written disk IO [min, max] )。提前下盘是指还有可用内存,但不足...
When an SQL statement is delivered, the QO compares the costs of redistribution and broadcast, and then generates an execution plan based on the algorithm. Optimization suggestion: If the table that you want to query is small and the instance contains a small number of shards, such as 5 ...
Checks all files on your hard disk and all running programs. Custom Enables users to scan specific drives and folders. Microsoft Defender Offline Reboots the device and runs a scan outside the Windows kernel. As a best practice, you should schedule a daily Quick scan. At any time,...