指向重复约束值的Upsert错误（在冲突时执行更新）

Question

当我尝试在FROM语句中使用多个源时，Postgres 9.5中的ON CONFLICT DO UPDATE存在问题。

的示例工作代码：

INSERT INTO new.bookmonographs (citavi_id, abstract, createdon, edition, title, year) 
SELECT "ID", "Abstract", "CreatedOn"::timestamp, "Edition", "Title", "Year" 
FROM old."Reference" 
WHERE old."Reference"."ReferenceType" = 'Book' 
    AND old."Reference"."Year" IS NOT NULL 
    AND old."Reference"."Title" IS NOT NULL 
ON CONFLICT (citavi_id) DO UPDATE 
    SET (abstract, createdon, edition, title, year) = (excluded.abstract, excluded.createdon, excluded.edition, excluded.title, excluded.year) 
; 

故障代码：

INSERT INTO new.bookmonographs (citavi_id, abstract, createdon, edition, title, year) 
SELECT "ID", "Abstract", "CreatedOn"::timestamp, "Edition", "Title", "Year" 
FROM old."Reference", old."ReferenceAuthor" 
WHERE old."Reference"."ReferenceType" = 'Book' 
    AND old."Reference"."Year" IS NOT NULL 
    AND old."Reference"."Title" IS NOT NULL 
    AND old."ReferenceAuthor"."ReferenceID" = old."Reference"."ID" 
    --Year, Title and Author must be present in the data, otherwise the entry is deemed useless, hence won't be included 
ON CONFLICT (citavi_id) DO UPDATE 
    SET (abstract, createdon, edition, title, year) = (excluded.abstract, excluded.createdon, excluded.edition, excluded.title, excluded.year) 
; 

我在添加另一种原因是语句，并多了一个WHERE语句，以确保只条目有一个标题，年份和作者被插入到新的数据库中。 （如果旧的，“Reference”，“ID”存在于旧的“ReferenceAuthor”中，则为“ReferenceID”，则存在作者）。即使没有额外的WHERE语句，查询也是错误的。我在SELECT中指定的列仅存在于old."Reference"中，而不存在于old."ReferenceAuthor"中。 目前old."ReferenceAuthor"和old."Reference"没有唯一约束，对于bookmonographs的潮头约束条件是：

CONSTRAINT bookmonographs_pk PRIMARY KEY (bookmonographsid), 
CONSTRAINT bookmonographs_bookseries FOREIGN KEY (bookseriesid) 
     REFERENCES new.bookseries (bookseriesid) MATCH SIMPLE 
     ON UPDATE NO ACTION ON DELETE NO ACTION, 
CONSTRAINT bookmonographs_citaviid_unique UNIQUE (citavi_id) 

错误PSQL抛出：

ERROR: ON CONFLICT DO UPDATE command cannot affect row a second time HINT: Ensure that no rows proposed for insertion within the same command have duplicate constrained values. ********** Error **********

ERROR: ON CONFLICT DO UPDATE command cannot affect row a second time SQL state: 21000 Hint: Ensure that no rows proposed for insertion within the same command have duplicate constrained values.

我不知道什么是错呢，或者为什么提示指向重复的约束值。

Answer 1

的问题是由显然有些条目有多个作者的事实引起的。因此，您在写入的select查询中的内连接将为同一条目返回多行，并且INSERT ... ON CONFLICT不会那样。由于您只使用ReferenceAuthor表进行过滤，因此您可以简单地重写查询，以便它通过在关联的子查询上执行exists来仅过滤没有任何作者的条目。方法如下：

INSERT INTO new.bookmonographs (citavi_id, abstract, createdon, edition, title, year) 
SELECT "ID", "Abstract", "CreatedOn"::timestamp, "Edition", "Title", "Year" 
FROM old."Reference" 
WHERE old."Reference"."ReferenceType" = 'Book' 
    AND old."Reference"."Year" IS NOT NULL 
    AND old."Reference"."Title" IS NOT NULL 
    AND exists(SELECT FROM old."ReferenceAuthor" WHERE old."ReferenceAuthor"."ReferenceID" = old."Reference"."ID") 
    --Year, Title and Author must be present in the data, otherwise the entry is deemed useless, hence won't be included 
ON CONFLICT (citavi_id) DO UPDATE 
    SET (abstract, createdon, edition, title, year) = (excluded.abstract, excluded.createdon, excluded.edition, excluded.title, excluded.year) 
; 

Answer 2

使用一个明确的INNER JOIN加入两个源表一起：

INSERT INTO new.bookmonographs (citavi_id, abstract, createdon, edition, title, year) 
SELECT "ID", "Abstract", "CreatedOn"::timestamp, "Edition", "Title", "Year" 
FROM old."Reference" 
INNER JOIN old."ReferenceAuthor"          -- explicit join 
    ON old."ReferenceAuthor"."ReferenceID" = old."Reference"."ID"  -- ON condition 
WHERE old."Reference"."ReferenceType" = 'Book' AND 
     old."Reference"."Year" IS NOT NULL  AND 
     old."Reference"."Title" IS NOT NULL 
ON CONFLICT (citavi_id) DO UPDATE 
SET (abstract, createdon, edition, title, year) = 
    (excluded.abstract, excluded.createdon, excluded.edition, excluded.title, 
    excluded.year)