diff --git a/synapse/storage/state_deltas.py b/synapse/storage/state_deltas.py
new file mode 100644
index 0000000000..57bc45cdb9
--- /dev/null
+++ b/synapse/storage/state_deltas.py
@@ -0,0 +1,74 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 Vector Creations Ltd
+#
+# 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.
+
+import logging
+
+from synapse.storage._base import SQLBaseStore
+
+logger = logging.getLogger(__name__)
+
+
+class StateDeltasStore(SQLBaseStore):
+
+ def get_current_state_deltas(self, prev_stream_id):
+ prev_stream_id = int(prev_stream_id)
+ if not self._curr_state_delta_stream_cache.has_any_entity_changed(prev_stream_id):
+ return []
+
+ def get_current_state_deltas_txn(txn):
+ # First we calculate the max stream id that will give us less than
+ # N results.
+ # We arbitarily limit to 100 stream_id entries to ensure we don't
+ # select toooo many.
+ sql = """
+ SELECT stream_id, count(*)
+ FROM current_state_delta_stream
+ WHERE stream_id > ?
+ GROUP BY stream_id
+ ORDER BY stream_id ASC
+ LIMIT 100
+ """
+ txn.execute(sql, (prev_stream_id,))
+
+ total = 0
+ max_stream_id = prev_stream_id
+ for max_stream_id, count in txn:
+ total += count
+ if total > 100:
+ # We arbitarily limit to 100 entries to ensure we don't
+ # select toooo many.
+ break
+
+ # Now actually get the deltas
+ sql = """
+ SELECT stream_id, room_id, type, state_key, event_id, prev_event_id
+ FROM current_state_delta_stream
+ WHERE ? < stream_id AND stream_id <= ?
+ ORDER BY stream_id ASC
+ """
+ txn.execute(sql, (prev_stream_id, max_stream_id,))
+ return self.cursor_to_dict(txn)
+
+ return self.runInteraction(
+ "get_current_state_deltas", get_current_state_deltas_txn
+ )
+
+ def get_max_stream_id_in_current_state_deltas(self):
+ return self._simple_select_one_onecol(
+ table="current_state_delta_stream",
+ keyvalues={},
+ retcol="COALESCE(MAX(stream_id), -1)",
+ desc="get_max_stream_id_in_current_state_deltas",
+ )
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