INSERT RETURNING 是否保证返回“正确"的东西?命令? [英] Is INSERT RETURNING guaranteed to return things in the "right" order?

问题描述

例子:

create table foo(
    id serial, 
    txt text
);

insert into foo(txt) values ('a'),('b'),('c') returning id;

返回:

 id 
----
  1
  2
  3
(3 rows)

似乎返回值中的 first id 将始终是 的 id'a'，第二个是 'b' 以此类推，但这是 insert into 的定义行为，还是可能会失败的巧合奇怪的情况?

It seems that the first id in the return value will always be the id for 'a', the second for 'b' and so on, but is this defined behaviour of insert into, or is it a coincidence that may fail under odd circumstances?

推荐答案

我在 保证 RETURNING 订单的文档 所以我认为你不能依赖它.奇怪的是 RETURNING 顺序将匹配 VALUES 顺序，但我看不到任何关于 VALUES 将插入哪个顺序的保证;VALUES 几乎肯定会按从左到右的顺序插入，但同样没有书面保证.

I don't see anything in the documentation that guarantees an order for RETURNING so I don't think you can depend on it. Odds are that the RETURNING order will match the VALUES order but I don't see any guarantees about what order the VALUES will be inserted in either; the VALUES are almost certainly going to be insert in order from left to right but again, there is no documented guarantee.

此外，关系模型是基于设置的，因此排序是用户应用的东西，而不是关系的固有属性.一般来说，如果无法明确指定排序，则没有隐含排序.

Also, the relational model is set based so ordering is something applied by the user rather than an inherent property of a relation. In general, if there is no way to explicitly specify an ordering, there is no implied ordering.

执行摘要:您所看到的顺序可能总是会发生，但不能保证，所以不要依赖它.

Execute summary: the ordering you're seeing is probably what will always happen but it is not guaranteed so don't depend on it.

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