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a2b4102a21
This commit adds a missing isolation test for (non-PERIOD) foreign keys. With REPEATABLE READ, one transaction can insert a referencing row while another deletes the referenced row, and both see a valid state. But after they have committed, the table violates referential integrity. If the INSERT precedes the DELETE, we use a crosscheck snapshot to see the just-added row, so that the DELETE can raise a foreign key error. You can see the table violate referential integrity if you change ri_restrict to pass false for detectNewRows to ri_PerformCheck. A crosscheck snapshot is not needed when the DELETE comes first, because the INSERT's trigger takes a FOR KEY SHARE lock that sees the row now marked for deletion, waits for that transaction to commit, and raises a serialization error. I (Paul) added a test for that too though. We already have a similar test (in ri-triggers.spec) for SERIALIZABLE snapshot isolation showing that you can implement foreign keys with just pl/pgSQL, but that test does nothing to validate ri_triggers.c. We also have tests (in fk-snapshot.spec) for other concurrency scenarios, but not this one: we test concurrently deleting both the referencing and referenced row, when the constraint activates a cascade/set null action. But those tests don't exercise ri_restrict, and the consequence of omitting a crosscheck comparison is different: a serialization failure, not a referential integrity violation. Author: Paul Jungwirth <pj@illuminatedcomputing.com> Reviewed-by: Rustam ALLAKOV <rustamallakov@gmail.com> Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com> Reviewed-by: Robert Haas <robertmhaas@gmail.com> Discussion: https://postgr.es/m/CA+renyUp=xja80rBaB6NpY3RRdi750y046x28bo_xg29zKY72Q@mail.gmail.com