Improve the performance of calculating ignored users in large rooms (#9024)

This allows for efficiently finding which users ignore a particular
user.

Co-authored-by: Erik Johnston <erik@matrix.org>

tests/storage/test_account_data.py

@@ -0,0 +1,120 @@
+# -*- coding: utf-8 -*-
+# Copyright 2021 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 Iterable, Set
+
+from synapse.api.constants import AccountDataTypes
+
+from tests import unittest
+
+
+class IgnoredUsersTestCase(unittest.HomeserverTestCase):
+    def prepare(self, hs, reactor, clock):
+        self.store = self.hs.get_datastore()
+        self.user = "@user:test"
+
+    def _update_ignore_list(
+        self, *ignored_user_ids: Iterable[str], ignorer_user_id: str = None
+    ) -> None:
+        """Update the account data to block the given users."""
+        if ignorer_user_id is None:
+            ignorer_user_id = self.user
+
+        self.get_success(
+            self.store.add_account_data_for_user(
+                ignorer_user_id,
+                AccountDataTypes.IGNORED_USER_LIST,
+                {"ignored_users": {u: {} for u in ignored_user_ids}},
+            )
+        )
+
+    def assert_ignorers(
+        self, ignored_user_id: str, expected_ignorer_user_ids: Set[str]
+    ) -> None:
+        self.assertEqual(
+            self.get_success(self.store.ignored_by(ignored_user_id)),
+            expected_ignorer_user_ids,
+        )
+
+    def test_ignoring_users(self):
+        """Basic adding/removing of users from the ignore list."""
+        self._update_ignore_list("@other:test", "@another:remote")
+
+        # Check a user which no one ignores.
+        self.assert_ignorers("@user:test", set())
+
+        # Check a local user which is ignored.
+        self.assert_ignorers("@other:test", {self.user})
+
+        # Check a remote user which is ignored.
+        self.assert_ignorers("@another:remote", {self.user})
+
+        # Add one user, remove one user, and leave one user.
+        self._update_ignore_list("@foo:test", "@another:remote")
+
+        # Check the removed user.
+        self.assert_ignorers("@other:test", set())
+
+        # Check the added user.
+        self.assert_ignorers("@foo:test", {self.user})
+
+        # Check the removed user.
+        self.assert_ignorers("@another:remote", {self.user})
+
+    def test_caching(self):
+        """Ensure that caching works properly between different users."""
+        # The first user ignores a user.
+        self._update_ignore_list("@other:test")
+        self.assert_ignorers("@other:test", {self.user})
+
+        # The second user ignores them.
+        self._update_ignore_list("@other:test", ignorer_user_id="@second:test")
+        self.assert_ignorers("@other:test", {self.user, "@second:test"})
+
+        # The first user un-ignores them.
+        self._update_ignore_list()
+        self.assert_ignorers("@other:test", {"@second:test"})
+
+    def test_invalid_data(self):
+        """Invalid data ends up clearing out the ignored users list."""
+        # Add some data and ensure it is there.
+        self._update_ignore_list("@other:test")
+        self.assert_ignorers("@other:test", {self.user})
+
+        # No ignored_users key.
+        self.get_success(
+            self.store.add_account_data_for_user(
+                self.user, AccountDataTypes.IGNORED_USER_LIST, {},
+            )
+        )
+
+        # No one ignores the user now.
+        self.assert_ignorers("@other:test", set())
+
+        # Add some data and ensure it is there.
+        self._update_ignore_list("@other:test")
+        self.assert_ignorers("@other:test", {self.user})
+
+        # Invalid data.
+        self.get_success(
+            self.store.add_account_data_for_user(
+                self.user,
+                AccountDataTypes.IGNORED_USER_LIST,
+                {"ignored_users": "unexpected"},
+            )
+        )
+
+        # No one ignores the user now.
+        self.assert_ignorers("@other:test", set())