PostgreSQL部分索引和UPSERT

经过谷歌搜索后,我的问题描述如下：

CREATE TABLE security (
  id          SERIAL PRIMARY KEY,vendor      VARCHAR(20),external_id VARCHAR(20),extinct     BOOLEAN DEFAULT FALSE
);

CREATE UNIQUE INDEX unique_vendor ON security(vendor,extinct) where vendor is not null;
CREATE UNIQUE INDEX unique_external_id ON security(external_id,extinct) where external_id is not null;

试图插入值：

insert into security (vendor,external_id,extinct) 
  values('Legion','LGNONE',false)
  ON CONFLICT(vendor,extinct) DO UPDATE
  SET vendor = 'Legion',external_id = 'LGNONE',extinct = false;

结果是：

[42P10] ERROR: there is no unique or exclusion constraint matching the ON CONFLICT specification

Altho这个工作(按规格)：

insert into security (vendor,extinct) 
    values('Legion',false)
    ON CONFLICT DO nothing;

PostgreSQL documentation stands that it should work

Postgresql v9.5

我的目标是找到在多个可空列上在此表上创建唯一索引的方法,并在UPSERT上使用新行更新旧行

冲突中使用的 conflict_target必须标识现有的唯一索引.你不能使用

on conflict (vendor,extinct)

因为三列上没有索引. Postgres结合多个索引以满足您的冲突目标并不是那么聪明.

但是,您可以像这样创建一个部分索引：

create unique index unique_vendor_external_id 
    on security(vendor,extinct) 
    where coalesce(vendor,external_id) is not null;

现在您可以将这三列用作冲突目标：

insert into security (vendor,false)
on conflict (vendor,extinct)          -- exact match to the index deFinition 
    where coalesce(vendor,external_id) is not null -- obligatory index_predicate
do update set
    vendor = excluded.vendor,external_id = excluded.external_id,extinct = excluded.extinct

注意排除使用特殊记录.对于文档：

The SET and WHERE clauses in ON CONFLICT DO UPDATE have access to the existing row using the table’s name (or an alias),and to rows proposed for insertion using the special excluded table.