标签
PostgreSQL , uuid , 无序uuid , 索引分裂 , io , 性能诊断
背景
无序UUID会带来很多问题,例如索引分裂膨胀,离散IO,WAL膨胀等,详见以前的分析。
Regular random UUIDs are distributed uniformly over the whole range of possible values.
标签
PostgreSQL , topn , topn.number_of_counters , count(*) group by order by count(*) desc limit x
背景
count(*) group by order by count(*) desc limit x 用来统计 topn。