摘要:

分析monetdb对于简单聚合的处理, 目的是排除其他算子和模块的干扰，以尽快梳理出对于聚合的操作.

DML

表结构及插入数据

create table b(b1 int, b2 varchar(2), primary key(b1)) ;create table a(a1 int, a2 varchar(2), foreign key(a1) references b(b1)) ;create table c(c1 int, c2 varchar(2)) ;create table d(d1 int, d2 varchar(2)) ;insert into a values(1, \'a1\');insert into a values(null, \'a2\');insert into a values(3, \'a3\');insert into b values(1, \'b1\');insert into b values(2, \'b2\');insert into b values(3, \'b3\');insert into c values(1, \'c1\');insert into c values(2, \'c2\');insert into c values(null, \'c3\');insert into d values(1, \'d1\');insert into d values(2, \'d2\');insert into d values(1, \'d3\');insert into d values(2, \'d4\');insert into d values(1, \'d3\');insert into d values(2