所以，如果我想要插入到外表中的一些记录，我可以这样做（伪代码）：
DO
INSERT INTO my_fdw_table VALUES next_row;
LOOP
或者这个：
INSERT INTO my_fdw_table SELECT all_the_rows;
根据我的直觉，第二个似乎更有效率，因为所有数据都是一次性发送的，SQL关键字重复次数较少。
然而，我不知道第二次是否会真正导致往返次数。如果有很多行，我也不知道或者第二个是否会冒某种语句长度限制的风险？
我正在使用postgres 9.3
答案 0 :(得分：0)
差异不会很大，因为即使是批量 SELECT
distinct(reservation.reservationid),reservation.name,reservation.age
as p_age,reservation.gender as
p_gender,reservation.lessonregistrationno,reservation.mobile,reservation.email,reservation.arrivaldate,reservation.arrivaltime,reservation.departuredate,reservation.departuretime,centers.name
as
centername,reservation.purposeofvisitid,reservation.otherpurpose,reservation.additionalinformation,reservation.status,reservation.membertype
as
type,reservation.iskriyaban,reservation.sharedacco,reservation.citizenship,reservation.total_guest,reservation.created,reservationmember.name
as
member_name,reservationmember.age,reservationmember.lessonregistrationnumber,reservationmember.gender,reservationmember.membertype,relationships.relationship,countries.name
as country,purposeofvisits.purpose FROM reservation LEFT JOIN centers
ON reservation.centerid = centers.centerid LEFT JOIN purposeofvisits
on purposeofvisits.purposeofvisitid = reservation.purposeofvisitid
LEFT JOIN countries ON countries.id = reservation.countryid LEFT JOIN
reservationmember on reservationmember.reservationid =
reservation.reservationid LEFT JOIN relationships on
reservationmember.relationshipid = relationships.relationshipid WHERE
1 AND ( (reservation.arrivaldate >= '2016-10-01') ) AND (
(reservation.arrivaldate <= '2016-10-10') ) ORDER BY
reservation.status desc, reservation.arrivaldate asc,
reservation.reservationid asc LIMIT 0, 25
也会在外部服务器上产生许多单INSERT个，因此在这两种情况下都会有相同数量的往返行程。 / p>
如果存在可衡量的差异，我怀疑是因为处理INSERT循环的客户端或PL / pgSQL代码需要一些时间。当然，如果你在自己的事务中运行每个INSERT或者在INSERT语句中使用动态SQL，那么你会因此而变慢。