count(distinct xx)优化 下面是针对count(distinct xx)写法的SQL优化案例: 测试数据准备: teledb=# CREATE TABLE t1(f1 serial not null unique,f2 text,f3 text,f4 text,f5 text,f6 text,f7 text,f8 text,f9 text,f10 text,f11 text,f12 text) distribute by shard(f1); NOTICE: Replica identity is needed for