SET約束的遞延未正常工作中的PostgreSQL 9.3

Question

如果我定義表a和b如下：

CREATE TABLE a(i integer); 
ALTER TABLE a ADD CONSTRAINT pkey_a PRIMARY KEY (i); 
CREATE TABLE b(j integer); 
ALTER TABLE b add CONSTRAINT fkey_ij FOREIGN KEY (j) 
     REFERENCES a (i) MATCH SIMPLE 
     ON UPDATE CASCADE ON DELETE CASCADE; 
INSERT INTO a(i) VALUES(1); 

然後執行以下操作：

START TRANSACTION; 
SET CONSTRAINTS ALL DEFERRED; 
INSERT INTO b(j) VALUES(2); 
INSERT INTO a(i) VALUES(2); 
COMMIT; 

它產生下面的錯誤。爲什麼SET CONSTRAINTS沒有達到預期效果？

ERROR: insert or update on table "b" violates foreign key constraint "fkey_ij"
SQL state: 23503 Detail: Key (j)=(2) is not present in table "a".

Answer 1

對於初學者，只有DEFERRABLE約束可以推遲。

但這不會幫助你的情況，因爲，FK限制不能彎曲這種方式在所有。 Per documentation：

Referential actions other than the NO ACTION check cannot be deferred, even if the constraint is declared deferrable.

反向您INSERT語句序列。

相關：

• Constraint defined DEFERRABLE INITIALLY IMMEDIATE is still DEFERRED?