Convert simple_select_list and simple_select_list_txn to return lists of tuples (#16505)

This should use fewer allocations and improves type hints.

19 files changed, 343 insertions, 263 deletions

diff --git a/synapse/storage/database.py b/synapse/storage/database.py
index 81f661160c..774d5c12f0 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -606,13 +606,16 @@ class DatabasePool:
 
         If the background updates have not completed, wait 15 sec and check again.
         """
-        updates = await self.simple_select_list(
-            "background_updates",
-            keyvalues=None,
-            retcols=["update_name"],
-            desc="check_background_updates",
+        updates = cast(
+            List[Tuple[str]],
+            await self.simple_select_list(
+                "background_updates",
+                keyvalues=None,
+                retcols=["update_name"],
+                desc="check_background_updates",
+            ),
         )
-        background_update_names = [x["update_name"] for x in updates]
+        background_update_names = [x[0] for x in updates]
 
         for table, update_name in UNIQUE_INDEX_BACKGROUND_UPDATES.items():
             if update_name not in background_update_names:
@@ -1804,9 +1807,9 @@ class DatabasePool:
         keyvalues: Optional[Dict[str, Any]],
         retcols: Collection[str],
         desc: str = "simple_select_list",
-    ) -> List[Dict[str, Any]]:
+    ) -> List[Tuple[Any, ...]]:
         """Executes a SELECT query on the named table, which may return zero or
-        more rows, returning the result as a list of dicts.
+        more rows, returning the result as a list of tuples.
 
         Args:
             table: the table name
@@ -1817,8 +1820,7 @@ class DatabasePool:
             desc: description of the transaction, for logging and metrics
 
         Returns:
-            A list of dictionaries, one per result row, each a mapping between the
-            column names from `retcols` and that column's value for the row.
+            A list of tuples, one per result row, each the retcolumn's value for the row.
         """
         return await self.runInteraction(
             desc,
@@ -1836,9 +1838,9 @@ class DatabasePool:
         table: str,
         keyvalues: Optional[Dict[str, Any]],
         retcols: Iterable[str],
-    ) -> List[Dict[str, Any]]:
+    ) -> List[Tuple[Any, ...]]:
         """Executes a SELECT query on the named table, which may return zero or
-        more rows, returning the result as a list of dicts.
+        more rows, returning the result as a list of tuples.
 
         Args:
             txn: Transaction object
@@ -1849,8 +1851,7 @@ class DatabasePool:
             retcols: the names of the columns to return
 
         Returns:
-            A list of dictionaries, one per result row, each a mapping between the
-            column names from `retcols` and that column's value for the row.
+            A list of tuples, one per result row, each the retcolumn's value for the row.
         """
         if keyvalues:
             sql = "SELECT %s FROM %s WHERE %s" % (
@@ -1863,7 +1864,7 @@ class DatabasePool:
             sql = "SELECT %s FROM %s" % (", ".join(retcols), table)
             txn.execute(sql)
 
-        return cls.cursor_to_dict(txn)
+        return txn.fetchall()
 
     async def simple_select_many_batch(
         self,
diff --git a/synapse/storage/databases/main/account_data.py b/synapse/storage/databases/main/account_data.py
index 84ef8136c2..d7482a1f4e 100644
--- a/synapse/storage/databases/main/account_data.py
+++ b/synapse/storage/databases/main/account_data.py
@@ -286,16 +286,20 @@ class AccountDataWorkerStore(PushRulesWorkerStore, CacheInvalidationWorkerStore)
 
         def get_account_data_for_room_txn(
             txn: LoggingTransaction,
-        ) -> Dict[str, JsonDict]:
-            rows = self.db_pool.simple_select_list_txn(
-                txn,
-                "room_account_data",
-                {"user_id": user_id, "room_id": room_id},
-                ["account_data_type", "content"],
+        ) -> Dict[str, JsonMapping]:
+            rows = cast(
+                List[Tuple[str, str]],
+                self.db_pool.simple_select_list_txn(
+                    txn,
+                    table="room_account_data",
+                    keyvalues={"user_id": user_id, "room_id": room_id},
+                    retcols=["account_data_type", "content"],
+                ),
             )
 
             return {
-                row["account_data_type"]: db_to_json(row["content"]) for row in rows
+                account_data_type: db_to_json(content)
+                for account_data_type, content in rows
             }
 
         return await self.db_pool.runInteraction(
diff --git a/synapse/storage/databases/main/appservice.py b/synapse/storage/databases/main/appservice.py
index 073a99cd84..fa7d1c469a 100644
--- a/synapse/storage/databases/main/appservice.py
+++ b/synapse/storage/databases/main/appservice.py
@@ -197,16 +197,21 @@ class ApplicationServiceTransactionWorkerStore(
         Returns:
             A list of ApplicationServices, which may be empty.
         """
-        results = await self.db_pool.simple_select_list(
-            "application_services_state", {"state": state.value}, ["as_id"]
+        results = cast(
+            List[Tuple[str]],
+            await self.db_pool.simple_select_list(
+                table="application_services_state",
+                keyvalues={"state": state.value},
+                retcols=("as_id",),
+            ),
         )
         # NB: This assumes this class is linked with ApplicationServiceStore
         as_list = self.get_app_services()
         services = []
 
-        for res in results:
+        for (as_id,) in results:
             for service in as_list:
-                if service.id == res["as_id"]:
+                if service.id == as_id:
                     services.append(service)
         return services
 
diff --git a/synapse/storage/databases/main/client_ips.py b/synapse/storage/databases/main/client_ips.py
index 8be1511859..c006129625 100644
--- a/synapse/storage/databases/main/client_ips.py
+++ b/synapse/storage/databases/main/client_ips.py
@@ -508,21 +508,24 @@ class ClientIpWorkerStore(ClientIpBackgroundUpdateStore, MonthlyActiveUsersWorke
         if device_id is not None:
             keyvalues["device_id"] = device_id
 
-        res = await self.db_pool.simple_select_list(
-            table="devices",
-            keyvalues=keyvalues,
-            retcols=("user_id", "ip", "user_agent", "device_id", "last_seen"),
+        res = cast(
+            List[Tuple[str, Optional[str], Optional[str], str, Optional[int]]],
+            await self.db_pool.simple_select_list(
+                table="devices",
+                keyvalues=keyvalues,
+                retcols=("user_id", "ip", "user_agent", "device_id", "last_seen"),
+            ),
         )
 
         return {
-            (d["user_id"], d["device_id"]): DeviceLastConnectionInfo(
-                user_id=d["user_id"],
-                device_id=d["device_id"],
-                ip=d["ip"],
-                user_agent=d["user_agent"],
-                last_seen=d["last_seen"],
+            (user_id, device_id): DeviceLastConnectionInfo(
+                user_id=user_id,
+                device_id=device_id,
+                ip=ip,
+                user_agent=user_agent,
+                last_seen=last_seen,
             )
-            for d in res
+            for user_id, ip, user_agent, device_id, last_seen in res
         }
 
     async def _get_user_ip_and_agents_from_database(
diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index fc23d18eba..0b75f6763a 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -283,7 +283,9 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
             allow_none=True,
         )
 
-    async def get_devices_by_user(self, user_id: str) -> Dict[str, Dict[str, str]]:
+    async def get_devices_by_user(
+        self, user_id: str
+    ) -> Dict[str, Dict[str, Optional[str]]]:
         """Retrieve all of a user's registered devices. Only returns devices
         that are not marked as hidden.
 
@@ -291,20 +293,26 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
             user_id:
         Returns:
             A mapping from device_id to a dict containing "device_id", "user_id"
-            and "display_name" for each device.
+            and "display_name" for each device. Display name may be null.
         """
-        devices = await self.db_pool.simple_select_list(
-            table="devices",
-            keyvalues={"user_id": user_id, "hidden": False},
-            retcols=("user_id", "device_id", "display_name"),
-            desc="get_devices_by_user",
+        devices = cast(
+            List[Tuple[str, str, Optional[str]]],
+            await self.db_pool.simple_select_list(
+                table="devices",
+                keyvalues={"user_id": user_id, "hidden": False},
+                retcols=("user_id", "device_id", "display_name"),
+                desc="get_devices_by_user",
+            ),
         )
 
-        return {d["device_id"]: d for d in devices}
+        return {
+            d[1]: {"user_id": d[0], "device_id": d[1], "display_name": d[2]}
+            for d in devices
+        }
 
     async def get_devices_by_auth_provider_session_id(
         self, auth_provider_id: str, auth_provider_session_id: str
-    ) -> List[Dict[str, Any]]:
+    ) -> List[Tuple[str, str]]:
         """Retrieve the list of devices associated with a SSO IdP session ID.
 
         Args:
@@ -313,14 +321,17 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
         Returns:
             A list of dicts containing the device_id and the user_id of each device
         """
-        return await self.db_pool.simple_select_list(
-            table="device_auth_providers",
-            keyvalues={
-                "auth_provider_id": auth_provider_id,
-                "auth_provider_session_id": auth_provider_session_id,
-            },
-            retcols=("user_id", "device_id"),
-            desc="get_devices_by_auth_provider_session_id",
+        return cast(
+            List[Tuple[str, str]],
+            await self.db_pool.simple_select_list(
+                table="device_auth_providers",
+                keyvalues={
+                    "auth_provider_id": auth_provider_id,
+                    "auth_provider_session_id": auth_provider_session_id,
+                },
+                retcols=("user_id", "device_id"),
+                desc="get_devices_by_auth_provider_session_id",
+            ),
         )
 
     @trace
@@ -821,15 +832,16 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
     async def get_cached_devices_for_user(
         self, user_id: str
     ) -> Mapping[str, JsonMapping]:
-        devices = await self.db_pool.simple_select_list(
-            table="device_lists_remote_cache",
-            keyvalues={"user_id": user_id},
-            retcols=("device_id", "content"),
-            desc="get_cached_devices_for_user",
+        devices = cast(
+            List[Tuple[str, str]],
+            await self.db_pool.simple_select_list(
+                table="device_lists_remote_cache",
+                keyvalues={"user_id": user_id},
+                retcols=("device_id", "content"),
+                desc="get_cached_devices_for_user",
+            ),
         )
-        return {
-            device["device_id"]: db_to_json(device["content"]) for device in devices
-        }
+        return {device[0]: db_to_json(device[1]) for device in devices}
 
     def get_cached_device_list_changes(
         self,
@@ -1080,7 +1092,7 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
             The IDs of users whose device lists need resync.
         """
         if user_ids:
-            row_tuples = cast(
+            rows = cast(
                 List[Tuple[str]],
                 await self.db_pool.simple_select_many_batch(
                     table="device_lists_remote_resync",
@@ -1090,11 +1102,9 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
                     desc="get_user_ids_requiring_device_list_resync_with_iterable",
                 ),
             )
-
-            return {row[0] for row in row_tuples}
         else:
             rows = cast(
-                List[Dict[str, str]],
+                List[Tuple[str]],
                 await self.db_pool.simple_select_list(
                     table="device_lists_remote_resync",
                     keyvalues=None,
@@ -1103,7 +1113,7 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
                 ),
             )
 
-            return {row["user_id"] for row in rows}
+        return {row[0] for row in rows}
 
     async def mark_remote_users_device_caches_as_stale(
         self, user_ids: StrCollection
diff --git a/synapse/storage/databases/main/e2e_room_keys.py b/synapse/storage/databases/main/e2e_room_keys.py
index aac4cfb054..ad904a26a6 100644
--- a/synapse/storage/databases/main/e2e_room_keys.py
+++ b/synapse/storage/databases/main/e2e_room_keys.py
@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import TYPE_CHECKING, Dict, Iterable, Mapping, Optional, Tuple, cast
+from typing import TYPE_CHECKING, Dict, Iterable, List, Mapping, Optional, Tuple, cast
 
 from typing_extensions import Literal, TypedDict
 
@@ -274,32 +274,41 @@ class EndToEndRoomKeyStore(EndToEndRoomKeyBackgroundStore):
             if session_id:
                 keyvalues["session_id"] = session_id
 
-        rows = await self.db_pool.simple_select_list(
-            table="e2e_room_keys",
-            keyvalues=keyvalues,
-            retcols=(
-                "user_id",
-                "room_id",
-                "session_id",
-                "first_message_index",
-                "forwarded_count",
-                "is_verified",
-                "session_data",
+        rows = cast(
+            List[Tuple[str, str, int, int, int, str]],
+            await self.db_pool.simple_select_list(
+                table="e2e_room_keys",
+                keyvalues=keyvalues,
+                retcols=(
+                    "room_id",
+                    "session_id",
+                    "first_message_index",
+                    "forwarded_count",
+                    "is_verified",
+                    "session_data",
+                ),
+                desc="get_e2e_room_keys",
             ),
-            desc="get_e2e_room_keys",
         )
 
         sessions: Dict[
             Literal["rooms"], Dict[str, Dict[Literal["sessions"], Dict[str, RoomKey]]]
         ] = {"rooms": {}}
-        for row in rows:
-            room_entry = sessions["rooms"].setdefault(row["room_id"], {"sessions": {}})
-            room_entry["sessions"][row["session_id"]] = {
-                "first_message_index": row["first_message_index"],
-                "forwarded_count": row["forwarded_count"],
+        for (
+            room_id,
+            session_id,
+            first_message_index,
+            forwarded_count,
+            is_verified,
+            session_data,
+        ) in rows:
+            room_entry = sessions["rooms"].setdefault(room_id, {"sessions": {}})
+            room_entry["sessions"][session_id] = {
+                "first_message_index": first_message_index,
+                "forwarded_count": forwarded_count,
                 # is_verified must be returned to the client as a boolean
-                "is_verified": bool(row["is_verified"]),
-                "session_data": db_to_json(row["session_data"]),
+                "is_verified": bool(is_verified),
+                "session_data": db_to_json(session_data),
             }
 
         return sessions
diff --git a/synapse/storage/databases/main/event_federation.py b/synapse/storage/databases/main/event_federation.py
index 4f80ce75cc..f1b0991503 100644
--- a/synapse/storage/databases/main/event_federation.py
+++ b/synapse/storage/databases/main/event_federation.py
@@ -1898,21 +1898,23 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas
         # keeping only the forward extremities (i.e. the events not referenced
         # by other events in the queue). We do this so that we can always
         # backpaginate in all the events we have dropped.
-        rows = await self.db_pool.simple_select_list(
-            table="federation_inbound_events_staging",
-            keyvalues={"room_id": room_id},
-            retcols=("event_id", "event_json"),
-            desc="prune_staged_events_in_room_fetch",
+        rows = cast(
+            List[Tuple[str, str]],
+            await self.db_pool.simple_select_list(
+                table="federation_inbound_events_staging",
+                keyvalues={"room_id": room_id},
+                retcols=("event_id", "event_json"),
+                desc="prune_staged_events_in_room_fetch",
+            ),
         )
 
         # Find the set of events referenced by those in the queue, as well as
         # collecting all the event IDs in the queue.
         referenced_events: Set[str] = set()
         seen_events: Set[str] = set()
-        for row in rows:
-            event_id = row["event_id"]
+        for event_id, event_json in rows:
             seen_events.add(event_id)
-            event_d = db_to_json(row["event_json"])
+            event_d = db_to_json(event_json)
 
             # We don't bother parsing the dicts into full blown event objects,
             # as that is needlessly expensive.
diff --git a/synapse/storage/databases/main/experimental_features.py b/synapse/storage/databases/main/experimental_features.py
index 654f924019..60621edeef 100644
--- a/synapse/storage/databases/main/experimental_features.py
+++ b/synapse/storage/databases/main/experimental_features.py
@@ -12,7 +12,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-from typing import TYPE_CHECKING, Dict, FrozenSet
+from typing import TYPE_CHECKING, Dict, FrozenSet, List, Tuple, cast
 
 from synapse.storage.database import DatabasePool, LoggingDatabaseConnection
 from synapse.storage.databases.main import CacheInvalidationWorkerStore
@@ -42,13 +42,16 @@ class ExperimentalFeaturesStore(CacheInvalidationWorkerStore):
         Returns:
             the features currently enabled for the user
         """
-        enabled = await self.db_pool.simple_select_list(
-            "per_user_experimental_features",
-            {"user_id": user_id, "enabled": True},
-            ["feature"],
+        enabled = cast(
+            List[Tuple[str]],
+            await self.db_pool.simple_select_list(
+                table="per_user_experimental_features",
+                keyvalues={"user_id": user_id, "enabled": True},
+                retcols=("feature",),
+            ),
         )
 
-        return frozenset(feature["feature"] for feature in enabled)
+        return frozenset(feature[0] for feature in enabled)
 
     async def set_features_for_user(
         self,
diff --git a/synapse/storage/databases/main/keys.py b/synapse/storage/databases/main/keys.py
index ea797864b9..ce88772f9e 100644
--- a/synapse/storage/databases/main/keys.py
+++ b/synapse/storage/databases/main/keys.py
@@ -248,17 +248,20 @@ class KeyStore(CacheInvalidationWorkerStore):
 
         If we have multiple entries for a given key ID, returns the most recent.
         """
-        rows = await self.db_pool.simple_select_list(
-            table="server_keys_json",
-            keyvalues={"server_name": server_name},
-            retcols=(
-                "key_id",
-                "from_server",
-                "ts_added_ms",
-                "ts_valid_until_ms",
-                "key_json",
+        rows = cast(
+            List[Tuple[str, str, int, int, Union[bytes, memoryview]]],
+            await self.db_pool.simple_select_list(
+                table="server_keys_json",
+                keyvalues={"server_name": server_name},
+                retcols=(
+                    "key_id",
+                    "from_server",
+                    "ts_added_ms",
+                    "ts_valid_until_ms",
+                    "key_json",
+                ),
+                desc="get_server_keys_json_for_remote",
             ),
-            desc="get_server_keys_json_for_remote",
         )
 
         if not rows:
@@ -266,14 +269,14 @@ class KeyStore(CacheInvalidationWorkerStore):
 
         # We sort the rows by ts_added_ms so that the most recently added entry
         # will stomp over older entries in the dictionary.
-        rows.sort(key=lambda r: r["ts_added_ms"])
+        rows.sort(key=lambda r: r[2])
 
         return {
-            row["key_id"]: FetchKeyResultForRemote(
+            key_id: FetchKeyResultForRemote(
                 # Cast to bytes since postgresql returns a memoryview.
-                key_json=bytes(row["key_json"]),
-                valid_until_ts=row["ts_valid_until_ms"],
-                added_ts=row["ts_added_ms"],
+                key_json=bytes(key_json),
+                valid_until_ts=ts_valid_until_ms,
+                added_ts=ts_added_ms,
             )
-            for row in rows
+            for key_id, from_server, ts_added_ms, ts_valid_until_ms, key_json in rows
         }
diff --git a/synapse/storage/databases/main/media_repository.py b/synapse/storage/databases/main/media_repository.py
index 2e6b176bd2..f82140b2e8 100644
--- a/synapse/storage/databases/main/media_repository.py
+++ b/synapse/storage/databases/main/media_repository.py
@@ -437,25 +437,24 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
         )
 
     async def get_local_media_thumbnails(self, media_id: str) -> List[ThumbnailInfo]:
-        rows = await self.db_pool.simple_select_list(
-            "local_media_repository_thumbnails",
-            {"media_id": media_id},
-            (
-                "thumbnail_width",
-                "thumbnail_height",
-                "thumbnail_method",
-                "thumbnail_type",
-                "thumbnail_length",
+        rows = cast(
+            List[Tuple[int, int, str, str, int]],
+            await self.db_pool.simple_select_list(
+                "local_media_repository_thumbnails",
+                {"media_id": media_id},
+                (
+                    "thumbnail_width",
+                    "thumbnail_height",
+                    "thumbnail_method",
+                    "thumbnail_type",
+                    "thumbnail_length",
+                ),
+                desc="get_local_media_thumbnails",
             ),
-            desc="get_local_media_thumbnails",
         )
         return [
             ThumbnailInfo(
-                width=row["thumbnail_width"],
-                height=row["thumbnail_height"],
-                method=row["thumbnail_method"],
-                type=row["thumbnail_type"],
-                length=row["thumbnail_length"],
+                width=row[0], height=row[1], method=row[2], type=row[3], length=row[4]
             )
             for row in rows
         ]
@@ -568,25 +567,24 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
     async def get_remote_media_thumbnails(
         self, origin: str, media_id: str
     ) -> List[ThumbnailInfo]:
-        rows = await self.db_pool.simple_select_list(
-            "remote_media_cache_thumbnails",
-            {"media_origin": origin, "media_id": media_id},
-            (
-                "thumbnail_width",
-                "thumbnail_height",
-                "thumbnail_method",
-                "thumbnail_type",
-                "thumbnail_length",
+        rows = cast(
+            List[Tuple[int, int, str, str, int]],
+            await self.db_pool.simple_select_list(
+                "remote_media_cache_thumbnails",
+                {"media_origin": origin, "media_id": media_id},
+                (
+                    "thumbnail_width",
+                    "thumbnail_height",
+                    "thumbnail_method",
+                    "thumbnail_type",
+                    "thumbnail_length",
+                ),
+                desc="get_remote_media_thumbnails",
             ),
-            desc="get_remote_media_thumbnails",
         )
         return [
             ThumbnailInfo(
-                width=row["thumbnail_width"],
-                height=row["thumbnail_height"],
-                method=row["thumbnail_method"],
-                type=row["thumbnail_type"],
-                length=row["thumbnail_length"],
+                width=row[0], height=row[1], method=row[2], type=row[3], length=row[4]
             )
             for row in rows
         ]
diff --git a/synapse/storage/databases/main/push_rule.py b/synapse/storage/databases/main/push_rule.py
index f5356e7f80..22025eca56 100644
--- a/synapse/storage/databases/main/push_rule.py
+++ b/synapse/storage/databases/main/push_rule.py
@@ -179,46 +179,44 @@ class PushRulesWorkerStore(
 
     @cached(max_entries=5000)
     async def get_push_rules_for_user(self, user_id: str) -> FilteredPushRules:
-        rows = await self.db_pool.simple_select_list(
-            table="push_rules",
-            keyvalues={"user_name": user_id},
-            retcols=(
-                "user_name",
-                "rule_id",
-                "priority_class",
-                "priority",
-                "conditions",
-                "actions",
+        rows = cast(
+            List[Tuple[str, int, int, str, str]],
+            await self.db_pool.simple_select_list(
+                table="push_rules",
+                keyvalues={"user_name": user_id},
+                retcols=(
+                    "rule_id",
+                    "priority_class",
+                    "priority",
+                    "conditions",
+                    "actions",
+                ),
+                desc="get_push_rules_for_user",
             ),
-            desc="get_push_rules_for_user",
         )
 
-        rows.sort(key=lambda row: (-int(row["priority_class"]), -int(row["priority"])))
+        # Sort by highest priority_class, then highest priority.
+        rows.sort(key=lambda row: (-int(row[1]), -int(row[2])))
 
         enabled_map = await self.get_push_rules_enabled_for_user(user_id)
 
         return _load_rules(
-            [
-                (
-                    row["rule_id"],
-                    row["priority_class"],
-                    row["conditions"],
-                    row["actions"],
-                )
-                for row in rows
-            ],
+            [(row[0], row[1], row[3], row[4]) for row in rows],
             enabled_map,
             self.hs.config.experimental,
         )
 
     async def get_push_rules_enabled_for_user(self, user_id: str) -> Dict[str, bool]:
-        results = await self.db_pool.simple_select_list(
-            table="push_rules_enable",
-            keyvalues={"user_name": user_id},
-            retcols=("rule_id", "enabled"),
-            desc="get_push_rules_enabled_for_user",
+        results = cast(
+            List[Tuple[str, Optional[Union[int, bool]]]],
+            await self.db_pool.simple_select_list(
+                table="push_rules_enable",
+                keyvalues={"user_name": user_id},
+                retcols=("rule_id", "enabled"),
+                desc="get_push_rules_enabled_for_user",
+            ),
         )
-        return {r["rule_id"]: bool(r["enabled"]) for r in results}
+        return {r[0]: bool(r[1]) for r in results}
 
     async def have_push_rules_changed_for_user(
         self, user_id: str, last_id: int
diff --git a/synapse/storage/databases/main/pusher.py b/synapse/storage/databases/main/pusher.py
index c7eb7fc478..a6a1671bd6 100644
--- a/synapse/storage/databases/main/pusher.py
+++ b/synapse/storage/databases/main/pusher.py
@@ -371,18 +371,20 @@ class PusherWorkerStore(SQLBaseStore):
     async def get_throttle_params_by_room(
         self, pusher_id: int
     ) -> Dict[str, ThrottleParams]:
-        res = await self.db_pool.simple_select_list(
-            "pusher_throttle",
-            {"pusher": pusher_id},
-            ["room_id", "last_sent_ts", "throttle_ms"],
-            desc="get_throttle_params_by_room",
+        res = cast(
+            List[Tuple[str, Optional[int], Optional[int]]],
+            await self.db_pool.simple_select_list(
+                "pusher_throttle",
+                {"pusher": pusher_id},
+                ["room_id", "last_sent_ts", "throttle_ms"],
+                desc="get_throttle_params_by_room",
+            ),
         )
 
         params_by_room = {}
-        for row in res:
-            params_by_room[row["room_id"]] = ThrottleParams(
-                row["last_sent_ts"],
-                row["throttle_ms"],
+        for room_id, last_sent_ts, throttle_ms in res:
+            params_by_room[room_id] = ThrottleParams(
+                last_sent_ts or 0, throttle_ms or 0
             )
 
         return params_by_room
diff --git a/synapse/storage/databases/main/registration.py b/synapse/storage/databases/main/registration.py
index 9e8643ae4d..b0ef7be155 100644
--- a/synapse/storage/databases/main/registration.py
+++ b/synapse/storage/databases/main/registration.py
@@ -855,13 +855,15 @@ class RegistrationWorkerStore(CacheInvalidationWorkerStore):
         Returns:
             Tuples of (auth_provider, external_id)
         """
-        res = await self.db_pool.simple_select_list(
-            table="user_external_ids",
-            keyvalues={"user_id": mxid},
-            retcols=("auth_provider", "external_id"),
-            desc="get_external_ids_by_user",
+        return cast(
+            List[Tuple[str, str]],
+            await self.db_pool.simple_select_list(
+                table="user_external_ids",
+                keyvalues={"user_id": mxid},
+                retcols=("auth_provider", "external_id"),
+                desc="get_external_ids_by_user",
+            ),
         )
-        return [(r["auth_provider"], r["external_id"]) for r in res]
 
     async def count_all_users(self) -> int:
         """Counts all users registered on the homeserver."""
@@ -997,13 +999,24 @@ class RegistrationWorkerStore(CacheInvalidationWorkerStore):
         )
 
     async def user_get_threepids(self, user_id: str) -> List[ThreepidResult]:
-        results = await self.db_pool.simple_select_list(
-            "user_threepids",
-            keyvalues={"user_id": user_id},
-            retcols=["medium", "address", "validated_at", "added_at"],
-            desc="user_get_threepids",
+        results = cast(
+            List[Tuple[str, str, int, int]],
+            await self.db_pool.simple_select_list(
+                "user_threepids",
+                keyvalues={"user_id": user_id},
+                retcols=["medium", "address", "validated_at", "added_at"],
+                desc="user_get_threepids",
+            ),
         )
-        return [ThreepidResult(**r) for r in results]
+        return [
+            ThreepidResult(
+                medium=r[0],
+                address=r[1],
+                validated_at=r[2],
+                added_at=r[3],
+            )
+            for r in results
+        ]
 
     async def user_delete_threepid(
         self, user_id: str, medium: str, address: str
@@ -1042,7 +1055,7 @@ class RegistrationWorkerStore(CacheInvalidationWorkerStore):
             desc="add_user_bound_threepid",
         )
 
-    async def user_get_bound_threepids(self, user_id: str) -> List[Dict[str, Any]]:
+    async def user_get_bound_threepids(self, user_id: str) -> List[Tuple[str, str]]:
         """Get the threepids that a user has bound to an identity server through the homeserver
         The homeserver remembers where binds to an identity server occurred. Using this
         method can retrieve those threepids.
@@ -1051,15 +1064,18 @@ class RegistrationWorkerStore(CacheInvalidationWorkerStore):
             user_id: The ID of the user to retrieve threepids for
 
         Returns:
-            List of dictionaries containing the following keys:
-                medium (str): The medium of the threepid (e.g "email")
-                address (str): The address of the threepid (e.g "bob@example.com")
-        """
-        return await self.db_pool.simple_select_list(
-            table="user_threepid_id_server",
-            keyvalues={"user_id": user_id},
-            retcols=["medium", "address"],
-            desc="user_get_bound_threepids",
+            List of tuples of two strings:
+                medium: The medium of the threepid (e.g "email")
+                address: The address of the threepid (e.g "bob@example.com")
+        """
+        return cast(
+            List[Tuple[str, str]],
+            await self.db_pool.simple_select_list(
+                table="user_threepid_id_server",
+                keyvalues={"user_id": user_id},
+                retcols=["medium", "address"],
+                desc="user_get_bound_threepids",
+            ),
         )
 
     async def remove_user_bound_threepid(
diff --git a/synapse/storage/databases/main/relations.py b/synapse/storage/databases/main/relations.py
index ce7bfd5146..419b2c7a22 100644
--- a/synapse/storage/databases/main/relations.py
+++ b/synapse/storage/databases/main/relations.py
@@ -384,14 +384,17 @@ class RelationsWorkerStore(SQLBaseStore):
         def get_all_relation_ids_for_event_txn(
             txn: LoggingTransaction,
         ) -> List[str]:
-            rows = self.db_pool.simple_select_list_txn(
-                txn=txn,
-                table="event_relations",
-                keyvalues={"relates_to_id": event_id},
-                retcols=["event_id"],
+            rows = cast(
+                List[Tuple[str]],
+                self.db_pool.simple_select_list_txn(
+                    txn=txn,
+                    table="event_relations",
+                    keyvalues={"relates_to_id": event_id},
+                    retcols=["event_id"],
+                ),
             )
 
-            return [row["event_id"] for row in rows]
+            return [row[0] for row in rows]
 
         return await self.db_pool.runInteraction(
             desc="get_all_relation_ids_for_event",
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
index 9d24d2c347..3e8fcf1975 100644
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -1232,28 +1232,30 @@ class RoomWorkerStore(CacheInvalidationWorkerStore):
         """
         room_servers: Dict[str, PartialStateResyncInfo] = {}
 
-        rows = await self.db_pool.simple_select_list(
-            table="partial_state_rooms",
-            keyvalues={},
-            retcols=("room_id", "joined_via"),
-            desc="get_server_which_served_partial_join",
+        rows = cast(
+            List[Tuple[str, str]],
+            await self.db_pool.simple_select_list(
+                table="partial_state_rooms",
+                keyvalues={},
+                retcols=("room_id", "joined_via"),
+                desc="get_server_which_served_partial_join",
+            ),
         )
 
-        for row in rows:
-            room_id = row["room_id"]
-            joined_via = row["joined_via"]
+        for room_id, joined_via in rows:
             room_servers[room_id] = PartialStateResyncInfo(joined_via=joined_via)
 
-        rows = await self.db_pool.simple_select_list(
-            "partial_state_rooms_servers",
-            keyvalues=None,
-            retcols=("room_id", "server_name"),
-            desc="get_partial_state_rooms",
+        rows = cast(
+            List[Tuple[str, str]],
+            await self.db_pool.simple_select_list(
+                "partial_state_rooms_servers",
+                keyvalues=None,
+                retcols=("room_id", "server_name"),
+                desc="get_partial_state_rooms",
+            ),
         )
 
-        for row in rows:
-            room_id = row["room_id"]
-            server_name = row["server_name"]
+        for room_id, server_name in rows:
             entry = room_servers.get(room_id)
             if entry is None:
                 # There is a foreign key constraint which enforces that every room_id in
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 3a87eba430..a1627dffb7 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -1070,13 +1070,16 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
         for fully-joined rooms.
         """
 
-        rows = await self.db_pool.simple_select_list(
-            "current_state_events",
-            keyvalues={"room_id": room_id},
-            retcols=("event_id", "membership"),
-            desc="has_completed_background_updates",
+        rows = cast(
+            List[Tuple[str, Optional[str]]],
+            await self.db_pool.simple_select_list(
+                "current_state_events",
+                keyvalues={"room_id": room_id},
+                retcols=("event_id", "membership"),
+                desc="has_completed_background_updates",
+            ),
         )
-        return {row["event_id"]: row["membership"] for row in rows}
+        return dict(rows)
 
     # TODO This returns a mutable object, which is generally confusing when using a cache.
     @cached(max_entries=10000)  # type: ignore[synapse-@cached-mutable]
diff --git a/synapse/storage/databases/main/tags.py b/synapse/storage/databases/main/tags.py
index 61403a98cf..7deda7790e 100644
--- a/synapse/storage/databases/main/tags.py
+++ b/synapse/storage/databases/main/tags.py
@@ -45,14 +45,17 @@ class TagsWorkerStore(AccountDataWorkerStore):
             tag content.
         """
 
-        rows = await self.db_pool.simple_select_list(
-            "room_tags", {"user_id": user_id}, ["room_id", "tag", "content"]
+        rows = cast(
+            List[Tuple[str, str, str]],
+            await self.db_pool.simple_select_list(
+                "room_tags", {"user_id": user_id}, ["room_id", "tag", "content"]
+            ),
         )
 
         tags_by_room: Dict[str, Dict[str, JsonDict]] = {}
-        for row in rows:
-            room_tags = tags_by_room.setdefault(row["room_id"], {})
-            room_tags[row["tag"]] = db_to_json(row["content"])
+        for room_id, tag, content in rows:
+            room_tags = tags_by_room.setdefault(room_id, {})
+            room_tags[tag] = db_to_json(content)
         return tags_by_room
 
     async def get_all_updated_tags(
@@ -161,13 +164,16 @@ class TagsWorkerStore(AccountDataWorkerStore):
         Returns:
             A mapping of tags to tag content.
         """
-        rows = await self.db_pool.simple_select_list(
-            table="room_tags",
-            keyvalues={"user_id": user_id, "room_id": room_id},
-            retcols=("tag", "content"),
-            desc="get_tags_for_room",
+        rows = cast(
+            List[Tuple[str, str]],
+            await self.db_pool.simple_select_list(
+                table="room_tags",
+                keyvalues={"user_id": user_id, "room_id": room_id},
+                retcols=("tag", "content"),
+                desc="get_tags_for_room",
+            ),
         )
-        return {row["tag"]: db_to_json(row["content"]) for row in rows}
+        return {tag: db_to_json(content) for tag, content in rows}
 
     async def add_tag_to_room(
         self, user_id: str, room_id: str, tag: str, content: JsonDict
diff --git a/synapse/storage/databases/main/ui_auth.py b/synapse/storage/databases/main/ui_auth.py
index 919c66f553..8ab7c42c4a 100644
--- a/synapse/storage/databases/main/ui_auth.py
+++ b/synapse/storage/databases/main/ui_auth.py
@@ -169,13 +169,17 @@ class UIAuthWorkerStore(SQLBaseStore):
             that auth-type.
         """
         results = {}
-        for row in await self.db_pool.simple_select_list(
-            table="ui_auth_sessions_credentials",
-            keyvalues={"session_id": session_id},
-            retcols=("stage_type", "result"),
-            desc="get_completed_ui_auth_stages",
-        ):
-            results[row["stage_type"]] = db_to_json(row["result"])
+        rows = cast(
+            List[Tuple[str, str]],
+            await self.db_pool.simple_select_list(
+                table="ui_auth_sessions_credentials",
+                keyvalues={"session_id": session_id},
+                retcols=("stage_type", "result"),
+                desc="get_completed_ui_auth_stages",
+            ),
+        )
+        for stage_type, result in rows:
+            results[stage_type] = db_to_json(result)
 
         return results
 
@@ -295,13 +299,15 @@ class UIAuthWorkerStore(SQLBaseStore):
         Returns:
             List of user_agent/ip pairs
         """
-        rows = await self.db_pool.simple_select_list(
-            table="ui_auth_sessions_ips",
-            keyvalues={"session_id": session_id},
-            retcols=("user_agent", "ip"),
-            desc="get_user_agents_ips_to_ui_auth_session",
+        return cast(
+            List[Tuple[str, str]],
+            await self.db_pool.simple_select_list(
+                table="ui_auth_sessions_ips",
+                keyvalues={"session_id": session_id},
+                retcols=("user_agent", "ip"),
+                desc="get_user_agents_ips_to_ui_auth_session",
+            ),
         )
-        return [(row["user_agent"], row["ip"]) for row in rows]
 
     async def delete_old_ui_auth_sessions(self, expiration_time: int) -> None:
         """
diff --git a/synapse/storage/databases/state/store.py b/synapse/storage/databases/state/store.py
index 09d2a8c5b3..182e429174 100644
--- a/synapse/storage/databases/state/store.py
+++ b/synapse/storage/databases/state/store.py
@@ -154,16 +154,22 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
             if not prev_group:
                 return _GetStateGroupDelta(None, None)
 
-            delta_ids = self.db_pool.simple_select_list_txn(
-                txn,
-                table="state_groups_state",
-                keyvalues={"state_group": state_group},
-                retcols=("type", "state_key", "event_id"),
+            delta_ids = cast(
+                List[Tuple[str, str, str]],
+                self.db_pool.simple_select_list_txn(
+                    txn,
+                    table="state_groups_state",
+                    keyvalues={"state_group": state_group},
+                    retcols=("type", "state_key", "event_id"),
+                ),
             )
 
             return _GetStateGroupDelta(
                 prev_group,
-                {(row["type"], row["state_key"]): row["event_id"] for row in delta_ids},
+                {
+                    (event_type, state_key): event_id
+                    for event_type, state_key, event_id in delta_ids
+                },
             )
 
         return await self.db_pool.runInteraction(