Fix background updates failing to add unique indexes on receipts (#14453)

As part of the database migration to support threaded receipts, there is
a possible window in between
`73/08thread_receipts_non_null.sql.postgres` removing the original
unique constraints on `receipts_linearized` and `receipts_graph` and the
`reeipts_linearized_unique_index` and `receipts_graph_unique_index`
background updates from `72/08thread_receipts.sql` completing where
the unique constraints on `receipts_linearized` and `receipts_graph` are
missing. Any emulated upserts on these tables must therefore be
performed with a lock held, otherwise duplicate rows can end up in the
tables when there are concurrent emulated upserts. Fix the missing lock.

Note that emulated upserts no longer happen by default on sqlite, since
the minimum supported version of sqlite supports native upserts by
default now.

Finally, clean up any duplicate receipts that may have crept in before
trying to create the `receipts_graph_unique_index` and
`receipts_linearized_unique_index` unique indexes.

Signed-off-by: Sean Quah <seanq@matrix.org>

1 files changed, 209 insertions, 0 deletions

diff --git a/tests/storage/databases/main/test_receipts.py b/tests/storage/databases/main/test_receipts.py
new file mode 100644
index 0000000000..c4f12d81d7
--- /dev/null
+++ b/tests/storage/databases/main/test_receipts.py
@@ -0,0 +1,209 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the 'License');
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an 'AS IS' BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from typing import Any, Dict, Optional, Sequence, Tuple
+
+from twisted.test.proto_helpers import MemoryReactor
+
+from synapse.rest import admin
+from synapse.rest.client import login, room
+from synapse.server import HomeServer
+from synapse.storage.database import LoggingTransaction
+from synapse.util import Clock
+
+from tests.unittest import HomeserverTestCase
+
+
+class ReceiptsBackgroundUpdateStoreTestCase(HomeserverTestCase):
+
+    servlets = [
+        admin.register_servlets,
+        room.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer):
+        self.store = hs.get_datastores().main
+        self.user_id = self.register_user("foo", "pass")
+        self.token = self.login("foo", "pass")
+        self.room_id = self.helper.create_room_as(self.user_id, tok=self.token)
+        self.other_room_id = self.helper.create_room_as(self.user_id, tok=self.token)
+
+    def _test_background_receipts_unique_index(
+        self,
+        update_name: str,
+        index_name: str,
+        table: str,
+        receipts: Dict[Tuple[str, str, str], Sequence[Dict[str, Any]]],
+        expected_unique_receipts: Dict[Tuple[str, str, str], Optional[Dict[str, Any]]],
+    ):
+        """Test that the background update to uniqueify non-thread receipts in
+        the given receipts table works properly.
+
+        Args:
+            update_name: The name of the background update to test.
+            index_name: The name of the index that the background update creates.
+            table: The table of receipts that the background update fixes.
+            receipts: The test data containing duplicate receipts.
+                A list of receipt rows to insert, grouped by
+                `(room_id, receipt_type, user_id)`.
+            expected_unique_receipts: A dictionary of `(room_id, receipt_type, user_id)`
+                keys and expected receipt key-values after duplicate receipts have been
+                removed.
+        """
+        # First, undo the background update.
+        def drop_receipts_unique_index(txn: LoggingTransaction) -> None:
+            txn.execute(f"DROP INDEX IF EXISTS {index_name}")
+
+        self.get_success(
+            self.store.db_pool.runInteraction(
+                "drop_receipts_unique_index",
+                drop_receipts_unique_index,
+            )
+        )
+
+        # Populate the receipts table, including duplicates.
+        for (room_id, receipt_type, user_id), rows in receipts.items():
+            for row in rows:
+                self.get_success(
+                    self.store.db_pool.simple_insert(
+                        table,
+                        {
+                            "room_id": room_id,
+                            "receipt_type": receipt_type,
+                            "user_id": user_id,
+                            "thread_id": None,
+                            "data": "{}",
+                            **row,
+                        },
+                    )
+                )
+
+        # Insert and run the background update.
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "background_updates",
+                {
+                    "update_name": update_name,
+                    "progress_json": "{}",
+                },
+            )
+        )
+
+        self.store.db_pool.updates._all_done = False
+
+        self.wait_for_background_updates()
+
+        # Check that the remaining receipts match expectations.
+        for (
+            room_id,
+            receipt_type,
+            user_id,
+        ), expected_row in expected_unique_receipts.items():
+            # Include the receipt key in the returned columns, for more informative
+            # assertion messages.
+            columns = ["room_id", "receipt_type", "user_id"]
+            if expected_row is not None:
+                columns += expected_row.keys()
+
+            rows = self.get_success(
+                self.store.db_pool.simple_select_list(
+                    table=table,
+                    keyvalues={
+                        "room_id": room_id,
+                        "receipt_type": receipt_type,
+                        "user_id": user_id,
+                        # `simple_select_onecol` does not support NULL filters,
+                        # so skip the filter on `thread_id`.
+                    },
+                    retcols=columns,
+                    desc="get_receipt",
+                )
+            )
+
+            if expected_row is not None:
+                self.assertEqual(
+                    len(rows),
+                    1,
+                    f"Background update did not leave behind latest receipt in {table}",
+                )
+                self.assertEqual(
+                    rows[0],
+                    {
+                        "room_id": room_id,
+                        "receipt_type": receipt_type,
+                        "user_id": user_id,
+                        **expected_row,
+                    },
+                )
+            else:
+                self.assertEqual(
+                    len(rows),
+                    0,
+                    f"Background update did not remove all duplicate receipts from {table}",
+                )
+
+    def test_background_receipts_linearized_unique_index(self):
+        """Test that the background update to uniqueify non-thread receipts in
+        `receipts_linearized` works properly.
+        """
+        self._test_background_receipts_unique_index(
+            "receipts_linearized_unique_index",
+            "receipts_linearized_unique_index",
+            "receipts_linearized",
+            receipts={
+                (self.room_id, "m.read", self.user_id): [
+                    {"stream_id": 5, "event_id": "$some_event"},
+                    {"stream_id": 6, "event_id": "$some_event"},
+                ],
+                (self.other_room_id, "m.read", self.user_id): [
+                    {"stream_id": 7, "event_id": "$some_event"}
+                ],
+            },
+            expected_unique_receipts={
+                (self.room_id, "m.read", self.user_id): {"stream_id": 6},
+                (self.other_room_id, "m.read", self.user_id): {"stream_id": 7},
+            },
+        )
+
+    def test_background_receipts_graph_unique_index(self):
+        """Test that the background update to uniqueify non-thread receipts in
+        `receipts_graph` works properly.
+        """
+        self._test_background_receipts_unique_index(
+            "receipts_graph_unique_index",
+            "receipts_graph_unique_index",
+            "receipts_graph",
+            receipts={
+                (self.room_id, "m.read", self.user_id): [
+                    {
+                        "event_ids": '["$some_event"]',
+                    },
+                    {
+                        "event_ids": '["$some_event"]',
+                    },
+                ],
+                (self.other_room_id, "m.read", self.user_id): [
+                    {
+                        "event_ids": '["$some_event"]',
+                    }
+                ],
+            },
+            expected_unique_receipts={
+                (self.room_id, "m.read", self.user_id): None,
+                (self.other_room_id, "m.read", self.user_id): {
+                    "event_ids": '["$some_event"]'
+                },
+            },
+        )