sql - Postgres : on conflict with implicit conflict target

Question

Postgres 10 和 11 的插入规范说:

ON CONFLICT [ conflict_target ] conflict_action

我有一张 table :

create table c (
    e text not null,
    m text not null,
    v numeric not null,
    PRIMARY KEY (e, m)
)

我想做

insert into candle values (...) 
    on conflict do update set
            v = 5

但是我得到一个错误:

ON CONFLICT DO UPDATE requires inference specification or constraint name Hint: For example, ON CONFLICT (column_name)

为什么我必须提供一个冲突的目标？如何提供主键或其他一些列集？

Answer 1

是的，<em>conflict_target</em>是可选的，但仅适用于 DO NOTHING .

根据 the documentation :

For ON CONFLICT DO NOTHING, it is optional to specify a <em>conflict_target</em>; when omitted, conflicts with all usable constraints (and unique indexes) are handled. For ON CONFLICT DO UPDATE, a <em>conflict_target</em> must be provided.