PostgreSQL join where 条件不同 explain 执行计划的差别

explain analyze
select
a.order_id, a.customer_id, a.price,
b.order_id, b.customer_id, b.customer_name
from
tbl_a a
left join
tbl_b b
--(select t.order_id from tbl_b t where t.order_id= 'oid1')b
on a.order_id = b.order_id
where
a.order_id = 'oid1'
--b.order_id = 'oid1'