"Kevin Grittner" <kevin.gritt...@wicourts.gov> writes:
>> What do you mean by referential integrity?  I don't believe you can
>> construct a foreign key problem at any transaction isolation level.
 
> I mean that if someone attempts to maintain referential integrity with
> SQL code, without using explicit locks, it is not reliable. 
> Presumably the implementation of foreign keys in PostgreSQL takes this
> into account and blocks the kind of behavior shown below.  This
> behavior would not occur with true serializable transactions.

IIRC the RI code has to fudge the normal serializable-snapshot behavior
in order to guarantee no constraint violation --- it has to be aware of
concurrent changes that would otherwise be invisible to a serializable
transaction.

                        regards, tom lane

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