8 files changed, 41 insertions, 23 deletions
diff --git a/synapse/storage/data_stores/main/cache.py b/synapse/storage/data_stores/main/cache.py
index 54ed8574c4..bf91512daf 100644
--- a/synapse/storage/data_stores/main/cache.py
+++ b/synapse/storage/data_stores/main/cache.py
@@ -21,7 +21,7 @@ from twisted.internet import defer
 
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.engines import PostgresEngine
-from synapse.util import batch_iter
+from synapse.util.iterutils import batch_iter
 
 logger = logging.getLogger(__name__)
 
diff --git a/synapse/storage/data_stores/main/devices.py b/synapse/storage/data_stores/main/devices.py
index 9a828231c4..f0a7962dd0 100644
--- a/synapse/storage/data_stores/main/devices.py
+++ b/synapse/storage/data_stores/main/devices.py
@@ -33,13 +33,13 @@ 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 (
     Cache,
     cached,
     cachedInlineCallbacks,
     cachedList,
 )
+from synapse.util.iterutils import batch_iter
 
 logger = logging.getLogger(__name__)
 
diff --git a/synapse/storage/data_stores/main/events.py b/synapse/storage/data_stores/main/events.py
index e9fe63037b..bb69c20448 100644
--- a/synapse/storage/data_stores/main/events.py
+++ b/synapse/storage/data_stores/main/events.py
@@ -43,9 +43,9 @@ 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
 from synapse.util.frozenutils import frozendict_json_encoder
+from synapse.util.iterutils import batch_iter
 
 logger = logging.getLogger(__name__)
 
diff --git a/synapse/storage/data_stores/main/events_worker.py b/synapse/storage/data_stores/main/events_worker.py
index 0cce5232f5..3b93e0597a 100644
--- a/synapse/storage/data_stores/main/events_worker.py
+++ b/synapse/storage/data_stores/main/events_worker.py
@@ -37,8 +37,8 @@ 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
+from synapse.util.iterutils import batch_iter
 from synapse.util.metrics import Measure
 
 logger = logging.getLogger(__name__)
diff --git a/synapse/storage/data_stores/main/keys.py b/synapse/storage/data_stores/main/keys.py
index 6b12f5a75f..ba89c68c9f 100644
--- a/synapse/storage/data_stores/main/keys.py
+++ b/synapse/storage/data_stores/main/keys.py
@@ -23,8 +23,8 @@ from signedjson.key import decode_verify_key_bytes
 
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.keys import FetchKeyResult
-from synapse.util import batch_iter
 from synapse.util.caches.descriptors import cached, cachedList
+from synapse.util.iterutils import batch_iter
 
 logger = logging.getLogger(__name__)
 
diff --git a/synapse/storage/data_stores/main/presence.py b/synapse/storage/data_stores/main/presence.py
index a2c83e0867..604c8b7ddd 100644
--- a/synapse/storage/data_stores/main/presence.py
+++ b/synapse/storage/data_stores/main/presence.py
@@ -17,8 +17,8 @@ from twisted.internet import defer
 
 from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
 from synapse.storage.presence import UserPresenceState
-from synapse.util import batch_iter
 from synapse.util.caches.descriptors import cached, cachedList
+from synapse.util.iterutils import batch_iter
 
 
 class PresenceStore(SQLBaseStore):
diff --git a/synapse/util/__init__.py b/synapse/util/__init__.py
index 7856353002..60f0de70f7 100644
--- a/synapse/util/__init__.py
+++ b/synapse/util/__init__.py
@@ -15,7 +15,6 @@
 
 import logging
 import re
-from itertools import islice
 
 import attr
 
@@ -107,22 +106,6 @@ class Clock(object):
                 raise
 
 
-def batch_iter(iterable, size):
-    """batch an iterable up into tuples with a maximum size
-
-    Args:
-        iterable (iterable): the iterable to slice
-        size (int): the maximum batch size
-
-    Returns:
-        an iterator over the chunks
-    """
-    # make sure we can deal with iterables like lists too
-    sourceiter = iter(iterable)
-    # call islice until it returns an empty tuple
-    return iter(lambda: tuple(islice(sourceiter, size)), ())
-
-
 def log_failure(failure, msg, consumeErrors=True):
     """Creates a function suitable for passing to `Deferred.addErrback` that
     logs any failures that occur.
diff --git a/synapse/util/iterutils.py b/synapse/util/iterutils.py
new file mode 100644
index 0000000000..c10016fbc5
--- /dev/null
+++ b/synapse/util/iterutils.py
@@ -0,0 +1,35 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2020 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from itertools import islice
+from typing import Iterable, Iterator, Sequence, Tuple, TypeVar
+
+T = TypeVar("T")
+
+
+def batch_iter(iterable: Iterable[T], size: int) -> Iterator[Tuple[T]]:
+    """batch an iterable up into tuples with a maximum size
+
+    Args:
+        iterable (iterable): the iterable to slice
+        size (int): the maximum batch size
+
+    Returns:
+        an iterator over the chunks
+    """
+    # make sure we can deal with iterables like lists too
+    sourceiter = iter(iterable)
+    # call islice until it returns an empty tuple
+    return iter(lambda: tuple(islice(sourceiter, size)), ())