以PG12为例，下面是演示demo

cd /opt/postgresql-12.7
./configure --prefix=/opt/pg12  --with-segsize=2
make  && make install
/opt/pg12/bin/initdb --pgdata=/home/postgres/data1207

初始化后可以通过以下命令查看segment size变为了2GB

插入数据来验证

create table test(id int,name text);
insert into test select n,n||'_test' from generate_series(1,40000000) n;