diff --git a/changelog.d/15907.misc b/changelog.d/15907.misc
new file mode 100644
index 0000000000..e0ecea6c2f
--- /dev/null
+++ b/changelog.d/15907.misc
@@ -0,0 +1 @@
+Add foreign key constraint to `event_forward_extremities`.
diff --git a/synapse/storage/background_updates.py b/synapse/storage/background_updates.py
index 5dce0a0159..2d5ddc3e7b 100644
--- a/synapse/storage/background_updates.py
+++ b/synapse/storage/background_updates.py
@@ -80,10 +80,14 @@ class ForeignKeyConstraint(Constraint):
Attributes:
referenced_table: The "parent" table name.
columns: The list of mappings of columns from table to referenced table
+ deferred: Whether to defer checking of the constraint to the end of the
+ transaction. This is useful for e.g. backwards compatibility where
+ an older version inserted data in the wrong order.
"""
referenced_table: str
columns: Sequence[Tuple[str, str]]
+ deferred: bool
def make_check_clause(self, table: str) -> str:
join_clause = " AND ".join(
@@ -94,7 +98,8 @@ class ForeignKeyConstraint(Constraint):
def make_constraint_clause_postgres(self) -> str:
column1_list = ", ".join(col1 for col1, col2 in self.columns)
column2_list = ", ".join(col2 for col1, col2 in self.columns)
- return f"FOREIGN KEY ({column1_list}) REFERENCES {self.referenced_table} ({column2_list})"
+ defer_clause = " DEFERRABLE INITIALLY DEFERRED" if self.deferred else ""
+ return f"FOREIGN KEY ({column1_list}) REFERENCES {self.referenced_table} ({column2_list}) {defer_clause}"
@attr.s(auto_attribs=True)
diff --git a/synapse/storage/databases/main/event_federation.py b/synapse/storage/databases/main/event_federation.py
index dabe603c8c..b2cda52ce5 100644
--- a/synapse/storage/databases/main/event_federation.py
+++ b/synapse/storage/databases/main/event_federation.py
@@ -146,7 +146,9 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas
update_name="event_forward_extremities_event_id_foreign_key_constraint_update",
table="event_forward_extremities",
constraint_name="event_forward_extremities_event_id",
- constraint=ForeignKeyConstraint("events", [("event_id", "event_id")]),
+ constraint=ForeignKeyConstraint(
+ "events", [("event_id", "event_id")], deferred=True
+ ),
unique_columns=("event_id", "room_id"),
)
diff --git a/synapse/storage/schema/main/delta/78/03event_extremities_constraints.py b/synapse/storage/schema/main/delta/78/03event_extremities_constraints.py
index f12e2a8f3e..bf8c57dbe8 100644
--- a/synapse/storage/schema/main/delta/78/03event_extremities_constraints.py
+++ b/synapse/storage/schema/main/delta/78/03event_extremities_constraints.py
@@ -28,19 +28,25 @@ FORWARD_EXTREMITIES_TABLE_SCHEMA = """
event_id TEXT NOT NULL,
room_id TEXT NOT NULL,
UNIQUE (event_id, room_id),
- CONSTRAINT event_forward_extremities_event_id FOREIGN KEY (event_id) REFERENCES events (event_id)
+ CONSTRAINT event_forward_extremities_event_id FOREIGN KEY (event_id) REFERENCES events (event_id) DEFERRABLE INITIALLY DEFERRED
)
"""
def run_create(cur: LoggingTransaction, database_engine: BaseDatabaseEngine) -> None:
+ # We mark this as a deferred constraint, as the previous version of Synapse
+ # inserted the event into the forward extremities *before* the events table.
+ # By marking as deferred we ensure that downgrading to the previous version
+ # will continue to work.
run_validate_constraint_and_delete_rows_schema_delta(
cur,
ordering=7803,
update_name="event_forward_extremities_event_id_foreign_key_constraint_update",
table="event_forward_extremities",
constraint_name="event_forward_extremities_event_id",
- constraint=ForeignKeyConstraint("events", [("event_id", "event_id")]),
+ constraint=ForeignKeyConstraint(
+ "events", [("event_id", "event_id")], deferred=True
+ ),
sqlite_table_name="event_forward_extremities2",
sqlite_table_schema=FORWARD_EXTREMITIES_TABLE_SCHEMA,
)
diff --git a/tests/storage/test_background_update.py b/tests/storage/test_background_update.py
index 6ca546f3f7..a4a823a252 100644
--- a/tests/storage/test_background_update.py
+++ b/tests/storage/test_background_update.py
@@ -586,7 +586,9 @@ class BackgroundUpdateValidateConstraintTestCase(unittest.HomeserverTestCase):
update_name="test_bg_update",
table="test_constraint",
constraint_name="test_constraint_name",
- constraint=ForeignKeyConstraint("base_table", [("b", "b")]),
+ constraint=ForeignKeyConstraint(
+ "base_table", [("b", "b")], deferred=False
+ ),
sqlite_table_name="test_constraint2",
sqlite_table_schema=table2_sqlite,
)
@@ -604,7 +606,9 @@ class BackgroundUpdateValidateConstraintTestCase(unittest.HomeserverTestCase):
"test_bg_update",
table="test_constraint",
constraint_name="test_constraint_name",
- constraint=ForeignKeyConstraint("base_table", [("b", "b")]),
+ constraint=ForeignKeyConstraint(
+ "base_table", [("b", "b")], deferred=False
+ ),
unique_columns=["a"],
)
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