Merge branch 'develop' of github.com:matrix-org/synapse into erikj/initial_sync_asnyc

34 files changed, 306 insertions, 198 deletions

diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py
index 8fb18203dc..ec89f645d4 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -49,15 +49,3 @@ class Storage(object):
         self.persistence = EventsPersistenceStorage(hs, stores)
         self.purge_events = PurgeEventsStorage(hs, stores)
         self.state = StateGroupStorage(hs, stores)
-
-
-def are_all_users_on_domain(txn, database_engine, domain):
-    sql = database_engine.convert_param_style(
-        "SELECT COUNT(*) FROM users WHERE name NOT LIKE ?"
-    )
-    pat = "%:" + domain
-    txn.execute(sql, (pat,))
-    num_not_matching = txn.fetchall()[0][0]
-    if num_not_matching == 0:
-        return True
-    return False
diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index b7e27d4e97..b7637b5dc0 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -37,11 +37,11 @@ class SQLBaseStore(object):
     per data store (and not one per physical database).
     """
 
-    def __init__(self, db_conn, hs):
+    def __init__(self, database: Database, db_conn, hs):
         self.hs = hs
         self._clock = hs.get_clock()
         self.database_engine = hs.database_engine
-        self.db = Database(hs)  # In future this will be passed in
+        self.db = database
         self.rand = random.SystemRandom()
 
     def _invalidate_state_caches(self, room_id, members_changed):
diff --git a/synapse/storage/background_updates.py b/synapse/storage/background_updates.py
index a9a13a2658..4f97fd5ab6 100644
--- a/synapse/storage/background_updates.py
+++ b/synapse/storage/background_updates.py
@@ -379,7 +379,7 @@ class BackgroundUpdater(object):
             logger.debug("[SQL] %s", sql)
             c.execute(sql)
 
-        if isinstance(self.db.database_engine, engines.PostgresEngine):
+        if isinstance(self.db.engine, engines.PostgresEngine):
             runner = create_index_psql
         elif psql_only:
             runner = None
diff --git a/synapse/storage/data_stores/__init__.py b/synapse/storage/data_stores/__init__.py
index cb184a98cc..cafedd5c0d 100644
--- a/synapse/storage/data_stores/__init__.py
+++ b/synapse/storage/data_stores/__init__.py
@@ -13,6 +13,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from synapse.storage.database import Database
+from synapse.storage.prepare_database import prepare_database
+
 
 class DataStores(object):
     """The various data stores.
@@ -20,7 +23,14 @@ class DataStores(object):
     These are low level interfaces to physical databases.
     """
 
-    def __init__(self, main_store, db_conn, hs):
-        # Note we pass in the main store here as workers use a different main
+    def __init__(self, main_store_class, db_conn, hs):
+        # Note we pass in the main store class here as workers use a different main
         # store.
-        self.main = main_store
+        database = Database(hs)
+
+        # Check that db is correctly configured.
+        database.engine.check_database(db_conn.cursor())
+
+        prepare_database(db_conn, database.engine, config=hs.config)
+
+        self.main = main_store_class(database, db_conn, hs)
diff --git a/synapse/storage/data_stores/main/__init__.py b/synapse/storage/data_stores/main/__init__.py
index 6adb8adb04..c577c0df5f 100644
--- a/synapse/storage/data_stores/main/__init__.py
+++ b/synapse/storage/data_stores/main/__init__.py
@@ -20,6 +20,7 @@ import logging
 import time
 
 from synapse.api.constants import PresenceState
+from synapse.storage.database import Database
 from synapse.storage.engines import PostgresEngine
 from synapse.storage.util.id_generators import (
     ChainedIdGenerator,
@@ -111,10 +112,20 @@ class DataStore(
     RelationsStore,
     CacheInvalidationStore,
 ):
-    def __init__(self, db_conn, hs):
+    def __init__(self, database: Database, db_conn, hs):
         self.hs = hs
         self._clock = hs.get_clock()
-        self.database_engine = hs.database_engine
+        self.database_engine = database.engine
+
+        all_users_native = are_all_users_on_domain(
+            db_conn.cursor(), database.engine, hs.hostname
+        )
+        if not all_users_native:
+            raise Exception(
+                "Found users in database not native to %s!\n"
+                "You cannot changed a synapse server_name after it's been configured"
+                % (hs.hostname,)
+            )
 
         self._stream_id_gen = StreamIdGenerator(
             db_conn,
@@ -169,7 +180,7 @@ class DataStore(
         else:
             self._cache_id_gen = None
 
-        super(DataStore, self).__init__(db_conn, hs)
+        super(DataStore, self).__init__(database, db_conn, hs)
 
         self._presence_on_startup = self._get_active_presence(db_conn)
 
@@ -554,3 +565,15 @@ class DataStore(
             retcols=["name", "password_hash", "is_guest", "admin", "user_type"],
             desc="search_users",
         )
+
+
+def are_all_users_on_domain(txn, database_engine, domain):
+    sql = database_engine.convert_param_style(
+        "SELECT COUNT(*) FROM users WHERE name NOT LIKE ?"
+    )
+    pat = "%:" + domain
+    txn.execute(sql, (pat,))
+    num_not_matching = txn.fetchall()[0][0]
+    if num_not_matching == 0:
+        return True
+    return False
diff --git a/synapse/storage/data_stores/main/account_data.py b/synapse/storage/data_stores/main/account_data.py
index 1a3dd7be8d..46b494b334 100644
--- a/synapse/storage/data_stores/main/account_data.py
+++ b/synapse/storage/data_stores/main/account_data.py
@@ -22,6 +22,7 @@ from canonicaljson import json
 from twisted.internet import defer
 
 from synapse.storage._base import SQLBaseStore
+from synapse.storage.database import Database
 from synapse.storage.util.id_generators import StreamIdGenerator
 from synapse.util.caches.descriptors import cached, cachedInlineCallbacks
 from synapse.util.caches.stream_change_cache import StreamChangeCache
@@ -38,13 +39,13 @@ class AccountDataWorkerStore(SQLBaseStore):
     # the abstract methods being implemented.
     __metaclass__ = abc.ABCMeta
 
-    def __init__(self, db_conn, hs):
+    def __init__(self, database: Database, db_conn, hs):
         account_max = self.get_max_account_data_stream_id()
         self._account_data_stream_cache = StreamChangeCache(
             "AccountDataAndTagsChangeCache", account_max
         )
 
-        super(AccountDataWorkerStore, self).__init__(db_conn, hs)
+        super(AccountDataWorkerStore, self).__init__(database, db_conn, hs)
 
     @abc.abstractmethod
     def get_max_account_data_stream_id(self):
@@ -270,12 +271,12 @@ class AccountDataWorkerStore(SQLBaseStore):
 
 
 class AccountDataStore(AccountDataWorkerStore):
-    def __init__(self, db_conn, hs):
+    def __init__(self, database: Database, db_conn, hs):
         self._account_data_id_gen = StreamIdGenerator(
             db_conn, "account_data_max_stream_id", "stream_id"
         )
 
-        super(AccountDataStore, self).__init__(db_conn, hs)
+        super(AccountDataStore, self).__init__(database, db_conn, hs)
 
     def get_max_account_data_stream_id(self):
         """Get the current max stream id for the private user data stream
diff --git a/synapse/storage/data_stores/main/appservice.py b/synapse/storage/data_stores/main/appservice.py
index 6b2e12719c..b2f39649fd 100644
--- a/synapse/storage/data_stores/main/appservice.py
+++ b/synapse/storage/data_stores/main/appservice.py
@@ -24,6 +24,7 @@ from synapse.appservice import AppServiceTransaction
 from synapse.config.appservice import load_appservices
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.data_stores.main.events_worker import EventsWorkerStore
+from synapse.storage.database import Database
 
 logger = logging.getLogger(__name__)
 
@@ -48,13 +49,13 @@ def _make_exclusive_regex(services_cache):
 
 
 class ApplicationServiceWorkerStore(SQLBaseStore):
-    def __init__(self, db_conn, hs):
+    def __init__(self, database: Database, db_conn, hs):
         self.services_cache = load_appservices(
             hs.hostname, hs.config.app_service_config_files
         )
         self.exclusive_user_regex = _make_exclusive_regex(self.services_cache)
 
-        super(ApplicationServiceWorkerStore, self).__init__(db_conn, hs)
+        super(ApplicationServiceWorkerStore, self).__init__(database, db_conn, hs)
 
     def get_app_services(self):
         return self.services_cache
diff --git a/synapse/storage/data_stores/main/client_ips.py b/synapse/storage/data_stores/main/client_ips.py
index 7b470a58f1..add3037b69 100644
--- a/synapse/storage/data_stores/main/client_ips.py
+++ b/synapse/storage/data_stores/main/client_ips.py
@@ -21,6 +21,7 @@ from twisted.internet import defer
 
 from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.storage._base import SQLBaseStore
+from synapse.storage.database import Database
 from synapse.util.caches import CACHE_SIZE_FACTOR
 from synapse.util.caches.descriptors import Cache
 
@@ -33,8 +34,8 @@ LAST_SEEN_GRANULARITY = 120 * 1000
 
 
 class ClientIpBackgroundUpdateStore(SQLBaseStore):
-    def __init__(self, db_conn, hs):
-        super(ClientIpBackgroundUpdateStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(ClientIpBackgroundUpdateStore, self).__init__(database, db_conn, hs)
 
         self.db.updates.register_background_index_update(
             "user_ips_device_index",
@@ -363,13 +364,13 @@ class ClientIpBackgroundUpdateStore(SQLBaseStore):
 
 
 class ClientIpStore(ClientIpBackgroundUpdateStore):
-    def __init__(self, db_conn, hs):
+    def __init__(self, database: Database, db_conn, hs):
 
         self.client_ip_last_seen = Cache(
             name="client_ip_last_seen", keylen=4, max_entries=50000 * CACHE_SIZE_FACTOR
         )
 
-        super(ClientIpStore, self).__init__(db_conn, hs)
+        super(ClientIpStore, self).__init__(database, db_conn, hs)
 
         self.user_ips_max_age = hs.config.user_ips_max_age
 
@@ -450,16 +451,18 @@ class ClientIpStore(ClientIpBackgroundUpdateStore):
                 # Technically an access token might not be associated with
                 # a device so we need to check.
                 if device_id:
-                    self.db.simple_upsert_txn(
+                    # this is always an update rather than an upsert: the row should
+                    # already exist, and if it doesn't, that may be because it has been
+                    # deleted, and we don't want to re-create it.
+                    self.db.simple_update_txn(
                         txn,
                         table="devices",
                         keyvalues={"user_id": user_id, "device_id": device_id},
-                        values={
+                        updatevalues={
                             "user_agent": user_agent,
                             "last_seen": last_seen,
                             "ip": ip,
                         },
-                        lock=False,
                     )
             except Exception as e:
                 # Failed to upsert, log and continue
diff --git a/synapse/storage/data_stores/main/deviceinbox.py b/synapse/storage/data_stores/main/deviceinbox.py
index 3c9f09301a..85cfa16850 100644
--- a/synapse/storage/data_stores/main/deviceinbox.py
+++ b/synapse/storage/data_stores/main/deviceinbox.py
@@ -21,6 +21,7 @@ from twisted.internet import defer
 
 from synapse.logging.opentracing import log_kv, set_tag, trace
 from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
+from synapse.storage.database import Database
 from synapse.util.caches.expiringcache import ExpiringCache
 
 logger = logging.getLogger(__name__)
@@ -210,8 +211,8 @@ class DeviceInboxWorkerStore(SQLBaseStore):
 class DeviceInboxBackgroundUpdateStore(SQLBaseStore):
     DEVICE_INBOX_STREAM_ID = "device_inbox_stream_drop"
 
-    def __init__(self, db_conn, hs):
-        super(DeviceInboxBackgroundUpdateStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(DeviceInboxBackgroundUpdateStore, self).__init__(database, db_conn, hs)
 
         self.db.updates.register_background_index_update(
             "device_inbox_stream_index",
@@ -241,8 +242,8 @@ class DeviceInboxBackgroundUpdateStore(SQLBaseStore):
 class DeviceInboxStore(DeviceInboxWorkerStore, DeviceInboxBackgroundUpdateStore):
     DEVICE_INBOX_STREAM_ID = "device_inbox_stream_drop"
 
-    def __init__(self, db_conn, hs):
-        super(DeviceInboxStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(DeviceInboxStore, self).__init__(database, db_conn, hs)
 
         # Map of (user_id, device_id) to the last stream_id that has been
         # deleted up to. This is so that we can no op deletions.
diff --git a/synapse/storage/data_stores/main/devices.py b/synapse/storage/data_stores/main/devices.py
index 91ddaf137e..9a828231c4 100644
--- a/synapse/storage/data_stores/main/devices.py
+++ b/synapse/storage/data_stores/main/devices.py
@@ -31,6 +31,7 @@ from synapse.logging.opentracing import (
 )
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage._base import SQLBaseStore, db_to_json, make_in_list_sql_clause
+from synapse.storage.database import Database
 from synapse.types import get_verify_key_from_cross_signing_key
 from synapse.util import batch_iter
 from synapse.util.caches.descriptors import (
@@ -642,8 +643,8 @@ class DeviceWorkerStore(SQLBaseStore):
 
 
 class DeviceBackgroundUpdateStore(SQLBaseStore):
-    def __init__(self, db_conn, hs):
-        super(DeviceBackgroundUpdateStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(DeviceBackgroundUpdateStore, self).__init__(database, db_conn, hs)
 
         self.db.updates.register_background_index_update(
             "device_lists_stream_idx",
@@ -692,8 +693,8 @@ class DeviceBackgroundUpdateStore(SQLBaseStore):
 
 
 class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
-    def __init__(self, db_conn, hs):
-        super(DeviceStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(DeviceStore, self).__init__(database, db_conn, hs)
 
         # Map of (user_id, device_id) -> bool. If there is an entry that implies
         # the device exists.
diff --git a/synapse/storage/data_stores/main/event_federation.py b/synapse/storage/data_stores/main/event_federation.py
index 31d2e8eb28..1f517e8fad 100644
--- a/synapse/storage/data_stores/main/event_federation.py
+++ b/synapse/storage/data_stores/main/event_federation.py
@@ -28,6 +28,7 @@ from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
 from synapse.storage.data_stores.main.events_worker import EventsWorkerStore
 from synapse.storage.data_stores.main.signatures import SignatureWorkerStore
+from synapse.storage.database import Database
 from synapse.util.caches.descriptors import cached
 
 logger = logging.getLogger(__name__)
@@ -491,8 +492,8 @@ class EventFederationStore(EventFederationWorkerStore):
 
     EVENT_AUTH_STATE_ONLY = "event_auth_state_only"
 
-    def __init__(self, db_conn, hs):
-        super(EventFederationStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(EventFederationStore, self).__init__(database, db_conn, hs)
 
         self.db.updates.register_background_update_handler(
             self.EVENT_AUTH_STATE_ONLY, self._background_delete_non_state_event_auth
diff --git a/synapse/storage/data_stores/main/event_push_actions.py b/synapse/storage/data_stores/main/event_push_actions.py
index eec054cd48..9988a6d3fc 100644
--- a/synapse/storage/data_stores/main/event_push_actions.py
+++ b/synapse/storage/data_stores/main/event_push_actions.py
@@ -24,6 +24,7 @@ from twisted.internet import defer
 
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage._base import LoggingTransaction, SQLBaseStore
+from synapse.storage.database import Database
 from synapse.util.caches.descriptors import cachedInlineCallbacks
 
 logger = logging.getLogger(__name__)
@@ -68,8 +69,8 @@ def _deserialize_action(actions, is_highlight):
 
 
 class EventPushActionsWorkerStore(SQLBaseStore):
-    def __init__(self, db_conn, hs):
-        super(EventPushActionsWorkerStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(EventPushActionsWorkerStore, self).__init__(database, db_conn, hs)
 
         # These get correctly set by _find_stream_orderings_for_times_txn
         self.stream_ordering_month_ago = None
@@ -611,8 +612,8 @@ class EventPushActionsWorkerStore(SQLBaseStore):
 class EventPushActionsStore(EventPushActionsWorkerStore):
     EPA_HIGHLIGHT_INDEX = "epa_highlight_index"
 
-    def __init__(self, db_conn, hs):
-        super(EventPushActionsStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(EventPushActionsStore, self).__init__(database, db_conn, hs)
 
         self.db.updates.register_background_index_update(
             self.EPA_HIGHLIGHT_INDEX,
diff --git a/synapse/storage/data_stores/main/events.py b/synapse/storage/data_stores/main/events.py
index d644c82784..998bba1aad 100644
--- a/synapse/storage/data_stores/main/events.py
+++ b/synapse/storage/data_stores/main/events.py
@@ -41,6 +41,7 @@ from synapse.storage._base import make_in_list_sql_clause
 from synapse.storage.data_stores.main.event_federation import EventFederationStore
 from synapse.storage.data_stores.main.events_worker import EventsWorkerStore
 from synapse.storage.data_stores.main.state import StateGroupWorkerStore
+from synapse.storage.database import Database
 from synapse.types import RoomStreamToken, get_domain_from_id
 from synapse.util import batch_iter
 from synapse.util.caches.descriptors import cached, cachedInlineCallbacks
@@ -95,8 +96,8 @@ def _retry_on_integrity_error(func):
 class EventsStore(
     StateGroupWorkerStore, EventFederationStore, EventsWorkerStore,
 ):
-    def __init__(self, db_conn, hs):
-        super(EventsStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(EventsStore, self).__init__(database, db_conn, hs)
 
         # Collect metrics on the number of forward extremities that exist.
         # Counter of number of extremities to count
@@ -1038,20 +1039,25 @@ class EventsStore(
             },
         )
 
-    @defer.inlineCallbacks
-    def _censor_redactions(self):
+    async def _censor_redactions(self):
         """Censors all redactions older than the configured period that haven't
         been censored yet.
 
         By censor we mean update the event_json table with the redacted event.
-
-        Returns:
-            Deferred
         """
 
         if self.hs.config.redaction_retention_period is None:
             return
 
+        if not (
+            await self.db.updates.has_completed_background_update(
+                "redactions_have_censored_ts_idx"
+            )
+        ):
+            # We don't want to run this until the appropriate index has been
+            # created.
+            return
+
         before_ts = self._clock.time_msec() - self.hs.config.redaction_retention_period
 
         # We fetch all redactions that:
@@ -1073,15 +1079,15 @@ class EventsStore(
             LIMIT ?
         """
 
-        rows = yield self.db.execute(
+        rows = await self.db.execute(
             "_censor_redactions_fetch", None, sql, before_ts, 100
         )
 
         updates = []
 
         for redaction_id, event_id in rows:
-            redaction_event = yield self.get_event(redaction_id, allow_none=True)
-            original_event = yield self.get_event(
+            redaction_event = await self.get_event(redaction_id, allow_none=True)
+            original_event = await self.get_event(
                 event_id, allow_rejected=True, allow_none=True
             )
 
@@ -1114,7 +1120,7 @@ class EventsStore(
                     updatevalues={"have_censored": True},
                 )
 
-        yield self.db.runInteraction("_update_censor_txn", _update_censor_txn)
+        await self.db.runInteraction("_update_censor_txn", _update_censor_txn)
 
     def _censor_event_txn(self, txn, event_id, pruned_json):
         """Censor an event by replacing its JSON in the event_json table with the
diff --git a/synapse/storage/data_stores/main/events_bg_updates.py b/synapse/storage/data_stores/main/events_bg_updates.py
index cb1fc30c31..5177b71016 100644
--- a/synapse/storage/data_stores/main/events_bg_updates.py
+++ b/synapse/storage/data_stores/main/events_bg_updates.py
@@ -23,6 +23,7 @@ from twisted.internet import defer
 
 from synapse.api.constants import EventContentFields
 from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
+from synapse.storage.database import Database
 
 logger = logging.getLogger(__name__)
 
@@ -33,8 +34,8 @@ class EventsBackgroundUpdatesStore(SQLBaseStore):
     EVENT_FIELDS_SENDER_URL_UPDATE_NAME = "event_fields_sender_url"
     DELETE_SOFT_FAILED_EXTREMITIES = "delete_soft_failed_extremities"
 
-    def __init__(self, db_conn, hs):
-        super(EventsBackgroundUpdatesStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(EventsBackgroundUpdatesStore, self).__init__(database, db_conn, hs)
 
         self.db.updates.register_background_update_handler(
             self.EVENT_ORIGIN_SERVER_TS_NAME, self._background_reindex_origin_server_ts
@@ -89,6 +90,14 @@ class EventsBackgroundUpdatesStore(SQLBaseStore):
             "event_store_labels", self._event_store_labels
         )
 
+        self.db.updates.register_background_index_update(
+            "redactions_have_censored_ts_idx",
+            index_name="redactions_have_censored_ts",
+            table="redactions",
+            columns=["received_ts"],
+            where_clause="NOT have_censored",
+        )
+
     @defer.inlineCallbacks
     def _background_reindex_fields_sender(self, progress, batch_size):
         target_min_stream_id = progress["target_min_stream_id_inclusive"]
diff --git a/synapse/storage/data_stores/main/events_worker.py b/synapse/storage/data_stores/main/events_worker.py
index e041fc5eac..2c9142814c 100644
--- a/synapse/storage/data_stores/main/events_worker.py
+++ b/synapse/storage/data_stores/main/events_worker.py
@@ -19,8 +19,10 @@ import itertools
 import logging
 import threading
 from collections import namedtuple
+from typing import List, Optional
 
 from canonicaljson import json
+from constantly import NamedConstant, Names
 
 from twisted.internet import defer
 
@@ -33,6 +35,7 @@ from synapse.events.utils import prune_event
 from synapse.logging.context import LoggingContext, PreserveLoggingContext
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
+from synapse.storage.database import Database
 from synapse.types import get_domain_from_id
 from synapse.util import batch_iter
 from synapse.util.caches.descriptors import Cache
@@ -54,9 +57,19 @@ EVENT_QUEUE_TIMEOUT_S = 0.1  # Timeout when waiting for requests for events
 _EventCacheEntry = namedtuple("_EventCacheEntry", ("event", "redacted_event"))
 
 
+class EventRedactBehaviour(Names):
+    """
+    What to do when retrieving a redacted event from the database.
+    """
+
+    AS_IS = NamedConstant()
+    REDACT = NamedConstant()
+    BLOCK = NamedConstant()
+
+
 class EventsWorkerStore(SQLBaseStore):
-    def __init__(self, db_conn, hs):
-        super(EventsWorkerStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(EventsWorkerStore, self).__init__(database, db_conn, hs)
 
         self._get_event_cache = Cache(
             "*getEvent*", keylen=3, max_entries=hs.config.event_cache_size
@@ -124,25 +137,27 @@ class EventsWorkerStore(SQLBaseStore):
     @defer.inlineCallbacks
     def get_event(
         self,
-        event_id,
-        check_redacted=True,
-        get_prev_content=False,
-        allow_rejected=False,
-        allow_none=False,
-        check_room_id=None,
+        event_id: List[str],
+        redact_behaviour: EventRedactBehaviour = EventRedactBehaviour.REDACT,
+        get_prev_content: bool = False,
+        allow_rejected: bool = False,
+        allow_none: bool = False,
+        check_room_id: Optional[str] = None,
     ):
         """Get an event from the database by event_id.
 
         Args:
-            event_id (str): The event_id of the event to fetch
-            check_redacted (bool): If True, check if event has been redacted
-                and redact it.
-            get_prev_content (bool): If True and event is a state event,
+            event_id: The event_id of the event to fetch
+            redact_behaviour: Determine what to do with a redacted event. Possible values:
+                * AS_IS - Return the full event body with no redacted content
+                * REDACT - Return the event but with a redacted body
+                * DISALLOW - Do not return redacted events
+            get_prev_content: If True and event is a state event,
                 include the previous states content in the unsigned field.
-            allow_rejected (bool): If True return rejected events.
-            allow_none (bool): If True, return None if no event found, if
+            allow_rejected: If True return rejected events.
+            allow_none: If True, return None if no event found, if
                 False throw a NotFoundError
-            check_room_id (str|None): if not None, check the room of the found event.
+            check_room_id: if not None, check the room of the found event.
                 If there is a mismatch, behave as per allow_none.
 
         Returns:
@@ -153,7 +168,7 @@ class EventsWorkerStore(SQLBaseStore):
 
         events = yield self.get_events_as_list(
             [event_id],
-            check_redacted=check_redacted,
+            redact_behaviour=redact_behaviour,
             get_prev_content=get_prev_content,
             allow_rejected=allow_rejected,
         )
@@ -172,27 +187,30 @@ class EventsWorkerStore(SQLBaseStore):
     @defer.inlineCallbacks
     def get_events(
         self,
-        event_ids,
-        check_redacted=True,
-        get_prev_content=False,
-        allow_rejected=False,
+        event_ids: List[str],
+        redact_behaviour: EventRedactBehaviour = EventRedactBehaviour.REDACT,
+        get_prev_content: bool = False,
+        allow_rejected: bool = False,
     ):
         """Get events from the database
 
         Args:
-            event_ids (list): The event_ids of the events to fetch
-            check_redacted (bool): If True, check if event has been redacted
-                and redact it.
-            get_prev_content (bool): If True and event is a state event,
+            event_ids: The event_ids of the events to fetch
+            redact_behaviour: Determine what to do with a redacted event. Possible
+                values:
+                * AS_IS - Return the full event body with no redacted content
+                * REDACT - Return the event but with a redacted body
+                * DISALLOW - Do not return redacted events
+            get_prev_content: If True and event is a state event,
                 include the previous states content in the unsigned field.
-            allow_rejected (bool): If True return rejected events.
+            allow_rejected: If True return rejected events.
 
         Returns:
             Deferred : Dict from event_id to event.
         """
         events = yield self.get_events_as_list(
             event_ids,
-            check_redacted=check_redacted,
+            redact_behaviour=redact_behaviour,
             get_prev_content=get_prev_content,
             allow_rejected=allow_rejected,
         )
@@ -202,21 +220,23 @@ class EventsWorkerStore(SQLBaseStore):
     @defer.inlineCallbacks
     def get_events_as_list(
         self,
-        event_ids,
-        check_redacted=True,
-        get_prev_content=False,
-        allow_rejected=False,
+        event_ids: List[str],
+        redact_behaviour: EventRedactBehaviour = EventRedactBehaviour.REDACT,
+        get_prev_content: bool = False,
+        allow_rejected: bool = False,
     ):
         """Get events from the database and return in a list in the same order
         as given by `event_ids` arg.
 
         Args:
-            event_ids (list): The event_ids of the events to fetch
-            check_redacted (bool): If True, check if event has been redacted
-                and redact it.
-            get_prev_content (bool): If True and event is a state event,
+            event_ids: The event_ids of the events to fetch
+            redact_behaviour: Determine what to do with a redacted event. Possible values:
+                * AS_IS - Return the full event body with no redacted content
+                * REDACT - Return the event but with a redacted body
+                * DISALLOW - Do not return redacted events
+            get_prev_content: If True and event is a state event,
                 include the previous states content in the unsigned field.
-            allow_rejected (bool): If True return rejected events.
+            allow_rejected: If True, return rejected events.
 
         Returns:
             Deferred[list[EventBase]]: List of events fetched from the database. The
@@ -318,10 +338,14 @@ class EventsWorkerStore(SQLBaseStore):
                     # Update the cache to save doing the checks again.
                     entry.event.internal_metadata.recheck_redaction = False
 
-            if check_redacted and entry.redacted_event:
-                event = entry.redacted_event
-            else:
-                event = entry.event
+            event = entry.event
+
+            if entry.redacted_event:
+                if redact_behaviour == EventRedactBehaviour.BLOCK:
+                    # Skip this event
+                    continue
+                elif redact_behaviour == EventRedactBehaviour.REDACT:
+                    event = entry.redacted_event
 
             events.append(event)
 
diff --git a/synapse/storage/data_stores/main/media_repository.py b/synapse/storage/data_stores/main/media_repository.py
index 03c9c6f8ae..80ca36dedf 100644
--- a/synapse/storage/data_stores/main/media_repository.py
+++ b/synapse/storage/data_stores/main/media_repository.py
@@ -13,11 +13,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 from synapse.storage._base import SQLBaseStore
+from synapse.storage.database import Database
 
 
 class MediaRepositoryBackgroundUpdateStore(SQLBaseStore):
-    def __init__(self, db_conn, hs):
-        super(MediaRepositoryBackgroundUpdateStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(MediaRepositoryBackgroundUpdateStore, self).__init__(
+            database, db_conn, hs
+        )
 
         self.db.updates.register_background_index_update(
             update_name="local_media_repository_url_idx",
@@ -31,8 +34,8 @@ class MediaRepositoryBackgroundUpdateStore(SQLBaseStore):
 class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
     """Persistence for attachments and avatars"""
 
-    def __init__(self, db_conn, hs):
-        super(MediaRepositoryStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(MediaRepositoryStore, self).__init__(database, db_conn, hs)
 
     def get_local_media(self, media_id):
         """Get the metadata for a local piece of media
diff --git a/synapse/storage/data_stores/main/monthly_active_users.py b/synapse/storage/data_stores/main/monthly_active_users.py
index 34bf3a1880..27158534cb 100644
--- a/synapse/storage/data_stores/main/monthly_active_users.py
+++ b/synapse/storage/data_stores/main/monthly_active_users.py
@@ -17,6 +17,7 @@ import logging
 from twisted.internet import defer
 
 from synapse.storage._base import SQLBaseStore
+from synapse.storage.database import Database
 from synapse.util.caches.descriptors import cached
 
 logger = logging.getLogger(__name__)
@@ -27,13 +28,13 @@ LAST_SEEN_GRANULARITY = 60 * 60 * 1000
 
 
 class MonthlyActiveUsersStore(SQLBaseStore):
-    def __init__(self, dbconn, hs):
-        super(MonthlyActiveUsersStore, self).__init__(None, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(MonthlyActiveUsersStore, self).__init__(database, db_conn, hs)
         self._clock = hs.get_clock()
         self.hs = hs
         # Do not add more reserved users than the total allowable number
         self.db.new_transaction(
-            dbconn,
+            db_conn,
             "initialise_mau_threepids",
             [],
             [],
diff --git a/synapse/storage/data_stores/main/push_rule.py b/synapse/storage/data_stores/main/push_rule.py
index de682cc63a..5ba13aa973 100644
--- a/synapse/storage/data_stores/main/push_rule.py
+++ b/synapse/storage/data_stores/main/push_rule.py
@@ -27,6 +27,7 @@ from synapse.storage.data_stores.main.appservice import ApplicationServiceWorker
 from synapse.storage.data_stores.main.pusher import PusherWorkerStore
 from synapse.storage.data_stores.main.receipts import ReceiptsWorkerStore
 from synapse.storage.data_stores.main.roommember import RoomMemberWorkerStore
+from synapse.storage.database import Database
 from synapse.storage.push_rule import InconsistentRuleException, RuleNotFoundException
 from synapse.util.caches.descriptors import cachedInlineCallbacks, cachedList
 from synapse.util.caches.stream_change_cache import StreamChangeCache
@@ -72,8 +73,8 @@ class PushRulesWorkerStore(
     # the abstract methods being implemented.
     __metaclass__ = abc.ABCMeta
 
-    def __init__(self, db_conn, hs):
-        super(PushRulesWorkerStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(PushRulesWorkerStore, self).__init__(database, db_conn, hs)
 
         push_rules_prefill, push_rules_id = self.db.get_cache_dict(
             db_conn,
diff --git a/synapse/storage/data_stores/main/receipts.py b/synapse/storage/data_stores/main/receipts.py
index ac2d45bd5c..96e54d145e 100644
--- a/synapse/storage/data_stores/main/receipts.py
+++ b/synapse/storage/data_stores/main/receipts.py
@@ -22,6 +22,7 @@ from canonicaljson import json
 from twisted.internet import defer
 
 from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
+from synapse.storage.database import Database
 from synapse.storage.util.id_generators import StreamIdGenerator
 from synapse.util.caches.descriptors import cached, cachedInlineCallbacks, cachedList
 from synapse.util.caches.stream_change_cache import StreamChangeCache
@@ -38,8 +39,8 @@ class ReceiptsWorkerStore(SQLBaseStore):
     # the abstract methods being implemented.
     __metaclass__ = abc.ABCMeta
 
-    def __init__(self, db_conn, hs):
-        super(ReceiptsWorkerStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(ReceiptsWorkerStore, self).__init__(database, db_conn, hs)
 
         self._receipts_stream_cache = StreamChangeCache(
             "ReceiptsRoomChangeCache", self.get_max_receipt_stream_id()
@@ -315,14 +316,14 @@ class ReceiptsWorkerStore(SQLBaseStore):
 
 
 class ReceiptsStore(ReceiptsWorkerStore):
-    def __init__(self, db_conn, hs):
+    def __init__(self, database: Database, db_conn, hs):
         # We instantiate this first as the ReceiptsWorkerStore constructor
         # needs to be able to call get_max_receipt_stream_id
         self._receipts_id_gen = StreamIdGenerator(
             db_conn, "receipts_linearized", "stream_id"
         )
 
-        super(ReceiptsStore, self).__init__(db_conn, hs)
+        super(ReceiptsStore, self).__init__(database, db_conn, hs)
 
     def get_max_receipt_stream_id(self):
         return self._receipts_id_gen.get_current_token()
diff --git a/synapse/storage/data_stores/main/registration.py b/synapse/storage/data_stores/main/registration.py
index 1ef143c6d8..5e8ecac0ea 100644
--- a/synapse/storage/data_stores/main/registration.py
+++ b/synapse/storage/data_stores/main/registration.py
@@ -27,6 +27,7 @@ from synapse.api.constants import UserTypes
 from synapse.api.errors import Codes, StoreError, SynapseError, ThreepidValidationError
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage._base import SQLBaseStore
+from synapse.storage.database import Database
 from synapse.types import UserID
 from synapse.util.caches.descriptors import cached, cachedInlineCallbacks
 
@@ -36,8 +37,8 @@ logger = logging.getLogger(__name__)
 
 
 class RegistrationWorkerStore(SQLBaseStore):
-    def __init__(self, db_conn, hs):
-        super(RegistrationWorkerStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(RegistrationWorkerStore, self).__init__(database, db_conn, hs)
 
         self.config = hs.config
         self.clock = hs.get_clock()
@@ -794,8 +795,8 @@ class RegistrationWorkerStore(SQLBaseStore):
 
 
 class RegistrationBackgroundUpdateStore(RegistrationWorkerStore):
-    def __init__(self, db_conn, hs):
-        super(RegistrationBackgroundUpdateStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(RegistrationBackgroundUpdateStore, self).__init__(database, db_conn, hs)
 
         self.clock = hs.get_clock()
         self.config = hs.config
@@ -920,8 +921,8 @@ class RegistrationBackgroundUpdateStore(RegistrationWorkerStore):
 
 
 class RegistrationStore(RegistrationBackgroundUpdateStore):
-    def __init__(self, db_conn, hs):
-        super(RegistrationStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(RegistrationStore, self).__init__(database, db_conn, hs)
 
         self._account_validity = hs.config.account_validity
 
diff --git a/synapse/storage/data_stores/main/room.py b/synapse/storage/data_stores/main/room.py
index da42dae243..aa476d0fbf 100644
--- a/synapse/storage/data_stores/main/room.py
+++ b/synapse/storage/data_stores/main/room.py
@@ -29,6 +29,7 @@ from synapse.api.constants import EventTypes
 from synapse.api.errors import StoreError
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.data_stores.main.search import SearchStore
+from synapse.storage.database import Database
 from synapse.types import ThirdPartyInstanceID
 from synapse.util.caches.descriptors import cached, cachedInlineCallbacks
 
@@ -45,6 +46,11 @@ RatelimitOverride = collections.namedtuple(
 
 
 class RoomWorkerStore(SQLBaseStore):
+    def __init__(self, database: Database, db_conn, hs):
+        super(RoomWorkerStore, self).__init__(database, db_conn, hs)
+
+        self.config = hs.config
+
     def get_room(self, room_id):
         """Retrieve a room.
 
@@ -361,8 +367,8 @@ class RoomWorkerStore(SQLBaseStore):
 
 
 class RoomBackgroundUpdateStore(SQLBaseStore):
-    def __init__(self, db_conn, hs):
-        super(RoomBackgroundUpdateStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(RoomBackgroundUpdateStore, self).__init__(database, db_conn, hs)
 
         self.config = hs.config
 
@@ -440,8 +446,8 @@ class RoomBackgroundUpdateStore(SQLBaseStore):
 
 
 class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore, SearchStore):
-    def __init__(self, db_conn, hs):
-        super(RoomStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(RoomStore, self).__init__(database, db_conn, hs)
 
         self.config = hs.config
 
diff --git a/synapse/storage/data_stores/main/roommember.py b/synapse/storage/data_stores/main/roommember.py
index 929f6b0d39..92e3b9c512 100644
--- a/synapse/storage/data_stores/main/roommember.py
+++ b/synapse/storage/data_stores/main/roommember.py
@@ -32,6 +32,7 @@ from synapse.storage._base import (
     make_in_list_sql_clause,
 )
 from synapse.storage.data_stores.main.events_worker import EventsWorkerStore
+from synapse.storage.database import Database
 from synapse.storage.engines import Sqlite3Engine
 from synapse.storage.roommember import (
     GetRoomsForUserWithStreamOrdering,
@@ -54,8 +55,8 @@ _CURRENT_STATE_MEMBERSHIP_UPDATE_NAME = "current_state_events_membership"
 
 
 class RoomMemberWorkerStore(EventsWorkerStore):
-    def __init__(self, db_conn, hs):
-        super(RoomMemberWorkerStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(RoomMemberWorkerStore, self).__init__(database, db_conn, hs)
 
         # Is the current_state_events.membership up to date? Or is the
         # background update still running?
@@ -835,8 +836,8 @@ class RoomMemberWorkerStore(EventsWorkerStore):
 
 
 class RoomMemberBackgroundUpdateStore(SQLBaseStore):
-    def __init__(self, db_conn, hs):
-        super(RoomMemberBackgroundUpdateStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(RoomMemberBackgroundUpdateStore, self).__init__(database, db_conn, hs)
         self.db.updates.register_background_update_handler(
             _MEMBERSHIP_PROFILE_UPDATE_NAME, self._background_add_membership_profile
         )
@@ -991,8 +992,8 @@ class RoomMemberBackgroundUpdateStore(SQLBaseStore):
 
 
 class RoomMemberStore(RoomMemberWorkerStore, RoomMemberBackgroundUpdateStore):
-    def __init__(self, db_conn, hs):
-        super(RoomMemberStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(RoomMemberStore, self).__init__(database, db_conn, hs)
 
     def _store_room_members_txn(self, txn, events, backfilled):
         """Store a room member in the database.
diff --git a/synapse/storage/data_stores/main/schema/delta/56/redaction_censor.sql b/synapse/storage/data_stores/main/schema/delta/56/redaction_censor.sql
index fe51b02309..ea95db0ed7 100644
--- a/synapse/storage/data_stores/main/schema/delta/56/redaction_censor.sql
+++ b/synapse/storage/data_stores/main/schema/delta/56/redaction_censor.sql
@@ -14,4 +14,3 @@
  */
 
 ALTER TABLE redactions ADD COLUMN have_censored BOOL NOT NULL DEFAULT false;
-CREATE INDEX redactions_have_censored ON redactions(event_id) WHERE not have_censored;
diff --git a/synapse/storage/data_stores/main/schema/delta/56/redaction_censor2.sql b/synapse/storage/data_stores/main/schema/delta/56/redaction_censor2.sql
index 77a5eca499..49ce35d794 100644
--- a/synapse/storage/data_stores/main/schema/delta/56/redaction_censor2.sql
+++ b/synapse/storage/data_stores/main/schema/delta/56/redaction_censor2.sql
@@ -14,7 +14,9 @@
  */
 
 ALTER TABLE redactions ADD COLUMN received_ts BIGINT;
-CREATE INDEX redactions_have_censored_ts ON redactions(received_ts) WHERE not have_censored;
 
 INSERT INTO background_updates (update_name, progress_json) VALUES
   ('redactions_received_ts', '{}');
+
+INSERT INTO background_updates (update_name, progress_json) VALUES
+  ('redactions_have_censored_ts_idx', '{}');
diff --git a/synapse/storage/data_stores/main/schema/delta/56/redaction_censor4.sql b/synapse/storage/data_stores/main/schema/delta/56/redaction_censor4.sql
new file mode 100644
index 0000000000..b7550f6f4e
--- /dev/null
+++ b/synapse/storage/data_stores/main/schema/delta/56/redaction_censor4.sql
@@ -0,0 +1,16 @@
+/* Copyright 2019 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.
+ */
+
+DROP INDEX IF EXISTS redactions_have_censored;
diff --git a/synapse/storage/data_stores/main/schema/full_schemas/README.md b/synapse/storage/data_stores/main/schema/full_schemas/README.md
new file mode 100644
index 0000000000..bbd3f18604
--- /dev/null
+++ b/synapse/storage/data_stores/main/schema/full_schemas/README.md
@@ -0,0 +1,13 @@
+# Building full schema dumps
+
+These schemas need to be made from a database that has had all background updates run.
+
+To do so, use `scripts-dev/make_full_schema.sh`. This will produce
+`full.sql.postgres ` and `full.sql.sqlite` files.
+
+Ensure postgres is installed and your user has the ability to run bash commands
+such as `createdb`.
+
+```
+./scripts-dev/make_full_schema.sh -p postgres_username -o output_dir/
+```
diff --git a/synapse/storage/data_stores/main/schema/full_schemas/README.txt b/synapse/storage/data_stores/main/schema/full_schemas/README.txt
deleted file mode 100644
index d3f6401344..0000000000
--- a/synapse/storage/data_stores/main/schema/full_schemas/README.txt
+++ /dev/null
@@ -1,19 +0,0 @@
-Building full schema dumps
-==========================
-
-These schemas need to be made from a database that has had all background updates run.
-
-Postgres
---------
-
-$ pg_dump --format=plain --schema-only --no-tablespaces --no-acl --no-owner $DATABASE_NAME| sed -e '/^--/d' -e 's/public\.//g' -e '/^SET /d' -e '/^SELECT /d' > full.sql.postgres
-
-SQLite
-------
-
-$ sqlite3 $DATABASE_FILE ".schema" > full.sql.sqlite
-
-After
------
-
-Delete the CREATE statements for "sqlite_stat1", "schema_version", "applied_schema_deltas", and "applied_module_schemas".
\ No newline at end of file
diff --git a/synapse/storage/data_stores/main/search.py b/synapse/storage/data_stores/main/search.py
index ffa1817e64..dfb46ee0f8 100644
--- a/synapse/storage/data_stores/main/search.py
+++ b/synapse/storage/data_stores/main/search.py
@@ -25,6 +25,8 @@ from twisted.internet import defer
 
 from synapse.api.errors import SynapseError
 from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
+from synapse.storage.data_stores.main.events_worker import EventRedactBehaviour
+from synapse.storage.database import Database
 from synapse.storage.engines import PostgresEngine, Sqlite3Engine
 
 logger = logging.getLogger(__name__)
@@ -42,8 +44,8 @@ class SearchBackgroundUpdateStore(SQLBaseStore):
     EVENT_SEARCH_USE_GIST_POSTGRES_NAME = "event_search_postgres_gist"
     EVENT_SEARCH_USE_GIN_POSTGRES_NAME = "event_search_postgres_gin"
 
-    def __init__(self, db_conn, hs):
-        super(SearchBackgroundUpdateStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(SearchBackgroundUpdateStore, self).__init__(database, db_conn, hs)
 
         if not hs.config.enable_search:
             return
@@ -342,8 +344,8 @@ class SearchBackgroundUpdateStore(SQLBaseStore):
 
 
 class SearchStore(SearchBackgroundUpdateStore):
-    def __init__(self, db_conn, hs):
-        super(SearchStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(SearchStore, self).__init__(database, db_conn, hs)
 
     def store_event_search_txn(self, txn, event, key, value):
         """Add event to the search table
@@ -452,7 +454,12 @@ class SearchStore(SearchBackgroundUpdateStore):
 
         results = list(filter(lambda row: row["room_id"] in room_ids, results))
 
-        events = yield self.get_events_as_list([r["event_id"] for r in results])
+        # We set redact_behaviour to BLOCK here to prevent redacted events being returned in
+        # search results (which is a data leak)
+        events = yield self.get_events_as_list(
+            [r["event_id"] for r in results],
+            redact_behaviour=EventRedactBehaviour.BLOCK,
+        )
 
         event_map = {ev.event_id: ev for ev in events}
 
diff --git a/synapse/storage/data_stores/main/state.py b/synapse/storage/data_stores/main/state.py
index 7d5a9f8128..dcc6b43cdf 100644
--- a/synapse/storage/data_stores/main/state.py
+++ b/synapse/storage/data_stores/main/state.py
@@ -28,6 +28,7 @@ from synapse.events import EventBase
 from synapse.events.snapshot import EventContext
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.data_stores.main.events_worker import EventsWorkerStore
+from synapse.storage.database import Database
 from synapse.storage.engines import PostgresEngine
 from synapse.storage.state import StateFilter
 from synapse.util.caches import get_cache_factor_for, intern_string
@@ -213,8 +214,8 @@ class StateGroupWorkerStore(
     STATE_GROUP_INDEX_UPDATE_NAME = "state_group_state_type_index"
     CURRENT_STATE_INDEX_UPDATE_NAME = "current_state_members_idx"
 
-    def __init__(self, db_conn, hs):
-        super(StateGroupWorkerStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(StateGroupWorkerStore, self).__init__(database, db_conn, hs)
 
         # Originally the state store used a single DictionaryCache to cache the
         # event IDs for the state types in a given state group to avoid hammering
@@ -277,7 +278,7 @@ class StateGroupWorkerStore(
 
     @defer.inlineCallbacks
     def get_room_predecessor(self, room_id):
-        """Get the predecessor room of an upgraded room if one exists.
+        """Get the predecessor of an upgraded room if it exists.
         Otherwise return None.
 
         Args:
@@ -290,14 +291,22 @@ class StateGroupWorkerStore(
                     * room_id (str): The room ID of the predecessor room
                     * event_id (str): The ID of the tombstone event in the predecessor room
 
+                None if a predecessor key is not found, or is not a dictionary.
+
         Raises:
-            NotFoundError if the room is unknown
+            NotFoundError if the given room is unknown
         """
         # Retrieve the room's create event
         create_event = yield self.get_create_event_for_room(room_id)
 
-        # Return predecessor if present
-        return create_event.content.get("predecessor", None)
+        # Retrieve the predecessor key of the create event
+        predecessor = create_event.content.get("predecessor", None)
+
+        # Ensure the key is a dictionary
+        if not isinstance(predecessor, dict):
+            return None
+
+        return predecessor
 
     @defer.inlineCallbacks
     def get_create_event_for_room(self, room_id):
@@ -317,7 +326,7 @@ class StateGroupWorkerStore(
 
         # If we can't find the create event, assume we've hit a dead end
         if not create_id:
-            raise NotFoundError("Unknown room %s" % (room_id))
+            raise NotFoundError("Unknown room %s" % (room_id,))
 
         # Retrieve the room's create event and return
         create_event = yield self.get_event(create_id)
@@ -1029,8 +1038,8 @@ class StateBackgroundUpdateStore(StateGroupBackgroundUpdateStore):
     CURRENT_STATE_INDEX_UPDATE_NAME = "current_state_members_idx"
     EVENT_STATE_GROUP_INDEX_UPDATE_NAME = "event_to_state_groups_sg_index"
 
-    def __init__(self, db_conn, hs):
-        super(StateBackgroundUpdateStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(StateBackgroundUpdateStore, self).__init__(database, db_conn, hs)
         self.db.updates.register_background_update_handler(
             self.STATE_GROUP_DEDUPLICATION_UPDATE_NAME,
             self._background_deduplicate_state,
@@ -1245,8 +1254,8 @@ class StateStore(StateGroupWorkerStore, StateBackgroundUpdateStore):
       * `state_groups_state`: Maps state group to state events.
     """
 
-    def __init__(self, db_conn, hs):
-        super(StateStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(StateStore, self).__init__(database, db_conn, hs)
 
     def _store_event_state_mappings_txn(
         self, txn, events_and_contexts: Iterable[Tuple[EventBase, EventContext]]
diff --git a/synapse/storage/data_stores/main/stats.py b/synapse/storage/data_stores/main/stats.py
index 40579bf965..7bc186e9a1 100644
--- a/synapse/storage/data_stores/main/stats.py
+++ b/synapse/storage/data_stores/main/stats.py
@@ -22,6 +22,7 @@ from twisted.internet.defer import DeferredLock
 
 from synapse.api.constants import EventTypes, Membership
 from synapse.storage.data_stores.main.state_deltas import StateDeltasStore
+from synapse.storage.database import Database
 from synapse.storage.engines import PostgresEngine
 from synapse.util.caches.descriptors import cached
 
@@ -58,8 +59,8 @@ TYPE_TO_ORIGIN_TABLE = {"room": ("rooms", "room_id"), "user": ("users", "name")}
 
 
 class StatsStore(StateDeltasStore):
-    def __init__(self, db_conn, hs):
-        super(StatsStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(StatsStore, self).__init__(database, db_conn, hs)
 
         self.server_name = hs.hostname
         self.clock = self.hs.get_clock()
diff --git a/synapse/storage/data_stores/main/stream.py b/synapse/storage/data_stores/main/stream.py
index 2ff8c57109..140da8dad6 100644
--- a/synapse/storage/data_stores/main/stream.py
+++ b/synapse/storage/data_stores/main/stream.py
@@ -47,6 +47,7 @@ from twisted.internet import defer
 from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.data_stores.main.events_worker import EventsWorkerStore
+from synapse.storage.database import Database
 from synapse.storage.engines import PostgresEngine
 from synapse.types import RoomStreamToken
 from synapse.util.caches.stream_change_cache import StreamChangeCache
@@ -251,8 +252,8 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
 
     __metaclass__ = abc.ABCMeta
 
-    def __init__(self, db_conn, hs):
-        super(StreamWorkerStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(StreamWorkerStore, self).__init__(database, db_conn, hs)
 
         events_max = self.get_room_max_stream_ordering()
         event_cache_prefill, min_event_val = self.db.get_cache_dict(
diff --git a/synapse/storage/data_stores/main/transactions.py b/synapse/storage/data_stores/main/transactions.py
index c0d155a43c..5b07c2fbc0 100644
--- a/synapse/storage/data_stores/main/transactions.py
+++ b/synapse/storage/data_stores/main/transactions.py
@@ -24,6 +24,7 @@ from twisted.internet import defer
 
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage._base import SQLBaseStore, db_to_json
+from synapse.storage.database import Database
 from synapse.util.caches.expiringcache import ExpiringCache
 
 # py2 sqlite has buffer hardcoded as only binary type, so we must use it,
@@ -52,8 +53,8 @@ class TransactionStore(SQLBaseStore):
     """A collection of queries for handling PDUs.
     """
 
-    def __init__(self, db_conn, hs):
-        super(TransactionStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(TransactionStore, self).__init__(database, db_conn, hs)
 
         self._clock.looping_call(self._start_cleanup_transactions, 30 * 60 * 1000)
 
diff --git a/synapse/storage/data_stores/main/user_directory.py b/synapse/storage/data_stores/main/user_directory.py
index 62ffb34b29..90c180ec6d 100644
--- a/synapse/storage/data_stores/main/user_directory.py
+++ b/synapse/storage/data_stores/main/user_directory.py
@@ -21,6 +21,7 @@ from twisted.internet import defer
 from synapse.api.constants import EventTypes, JoinRules
 from synapse.storage.data_stores.main.state import StateFilter
 from synapse.storage.data_stores.main.state_deltas import StateDeltasStore
+from synapse.storage.database import Database
 from synapse.storage.engines import PostgresEngine, Sqlite3Engine
 from synapse.types import get_domain_from_id, get_localpart_from_id
 from synapse.util.caches.descriptors import cached
@@ -37,8 +38,8 @@ class UserDirectoryBackgroundUpdateStore(StateDeltasStore):
     # add_users_who_share_private_rooms?
     SHARE_PRIVATE_WORKING_SET = 500
 
-    def __init__(self, db_conn, hs):
-        super(UserDirectoryBackgroundUpdateStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(UserDirectoryBackgroundUpdateStore, self).__init__(database, db_conn, hs)
 
         self.server_name = hs.hostname
 
@@ -549,8 +550,8 @@ class UserDirectoryStore(UserDirectoryBackgroundUpdateStore):
     # add_users_who_share_private_rooms?
     SHARE_PRIVATE_WORKING_SET = 500
 
-    def __init__(self, db_conn, hs):
-        super(UserDirectoryStore, self).__init__(db_conn, hs)
+    def __init__(self, database: Database, db_conn, hs):
+        super(UserDirectoryStore, self).__init__(database, db_conn, hs)
 
     def remove_from_user_dir(self, user_id):
         def _remove_from_user_dir_txn(txn):
diff --git a/synapse/storage/database.py b/synapse/storage/database.py
index 6843b7e7f8..ec19ae1d9d 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -234,7 +234,7 @@ class Database(object):
         #   to watch it
         self._txn_perf_counters = PerformanceCounters()
 
-        self.database_engine = hs.database_engine
+        self.engine = hs.database_engine
 
         # A set of tables that are not safe to use native upserts in.
         self._unsafe_to_upsert_tables = set(UNIQUE_INDEX_BACKGROUND_UPDATES.keys())
@@ -242,10 +242,10 @@ class Database(object):
         # We add the user_directory_search table to the blacklist on SQLite
         # because the existing search table does not have an index, making it
         # unsafe to use native upserts.
-        if isinstance(self.database_engine, Sqlite3Engine):
+        if isinstance(self.engine, Sqlite3Engine):
             self._unsafe_to_upsert_tables.add("user_directory_search")
 
-        if self.database_engine.can_native_upsert:
+        if self.engine.can_native_upsert:
             # Check ASAP (and then later, every 1s) to see if we have finished
             # background updates of tables that aren't safe to update.
             self._clock.call_later(
@@ -331,7 +331,7 @@ class Database(object):
                 cursor = LoggingTransaction(
                     conn.cursor(),
                     name,
-                    self.database_engine,
+                    self.engine,
                     after_callbacks,
                     exception_callbacks,
                 )
@@ -339,7 +339,7 @@ class Database(object):
                     r = func(cursor, *args, **kwargs)
                     conn.commit()
                     return r
-                except self.database_engine.module.OperationalError as e:
+                except self.engine.module.OperationalError as e:
                     # This can happen if the database disappears mid
                     # transaction.
                     logger.warning(
@@ -353,20 +353,20 @@ class Database(object):
                         i += 1
                         try:
                             conn.rollback()
-                        except self.database_engine.module.Error as e1:
+                        except self.engine.module.Error as e1:
                             logger.warning(
                                 "[TXN EROLL] {%s} %s", name, exception_to_unicode(e1)
                             )
                         continue
                     raise
-                except self.database_engine.module.DatabaseError as e:
-                    if self.database_engine.is_deadlock(e):
+                except self.engine.module.DatabaseError as e:
+                    if self.engine.is_deadlock(e):
                         logger.warning("[TXN DEADLOCK] {%s} %d/%d", name, i, N)
                         if i < N:
                             i += 1
                             try:
                                 conn.rollback()
-                            except self.database_engine.module.Error as e1:
+                            except self.engine.module.Error as e1:
                                 logger.warning(
                                     "[TXN EROLL] {%s} %s",
                                     name,
@@ -494,7 +494,7 @@ class Database(object):
                 sql_scheduling_timer.observe(sched_duration_sec)
                 context.add_database_scheduled(sched_duration_sec)
 
-                if self.database_engine.is_connection_closed(conn):
+                if self.engine.is_connection_closed(conn):
                     logger.debug("Reconnecting closed database connection")
                     conn.reconnect()
 
@@ -561,7 +561,7 @@ class Database(object):
         """
         try:
             yield self.runInteraction(desc, self.simple_insert_txn, table, values)
-        except self.database_engine.module.IntegrityError:
+        except self.engine.module.IntegrityError:
             # We have to do or_ignore flag at this layer, since we can't reuse
             # a cursor after we receive an error from the db.
             if not or_ignore:
@@ -660,7 +660,7 @@ class Database(object):
                     lock=lock,
                 )
                 return result
-            except self.database_engine.module.IntegrityError as e:
+            except self.engine.module.IntegrityError as e:
                 attempts += 1
                 if attempts >= 5:
                     # don't retry forever, because things other than races
@@ -692,10 +692,7 @@ class Database(object):
             upserts return True if a new entry was created, False if an existing
             one was updated.
         """
-        if (
-            self.database_engine.can_native_upsert
-            and table not in self._unsafe_to_upsert_tables
-        ):
+        if self.engine.can_native_upsert and table not in self._unsafe_to_upsert_tables:
             return self.simple_upsert_txn_native_upsert(
                 txn, table, keyvalues, values, insertion_values=insertion_values
             )
@@ -726,7 +723,7 @@ class Database(object):
         """
         # We need to lock the table :(, unless we're *really* careful
         if lock:
-            self.database_engine.lock_table(txn, table)
+            self.engine.lock_table(txn, table)
 
         def _getwhere(key):
             # If the value we're passing in is None (aka NULL), we need to use
@@ -828,10 +825,7 @@ class Database(object):
         Returns:
             None
         """
-        if (
-            self.database_engine.can_native_upsert
-            and table not in self._unsafe_to_upsert_tables
-        ):
+        if self.engine.can_native_upsert and table not in self._unsafe_to_upsert_tables:
             return self.simple_upsert_many_txn_native_upsert(
                 txn, table, key_names, key_values, value_names, value_values
             )
@@ -1301,7 +1295,7 @@ class Database(object):
             "limit": limit,
         }
 
-        sql = self.database_engine.convert_param_style(sql)
+        sql = self.engine.convert_param_style(sql)
 
         txn = db_conn.cursor()
         txn.execute(sql, (int(max_value),))