3 files changed, 52 insertions, 18 deletions
diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py
index eb88842308..ee2153737d 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -45,9 +45,10 @@ from .search import SearchStore
 from .tags import TagsStore
 from .account_data import AccountDataStore
 
-
 from util.id_generators import IdGenerator, StreamIdGenerator
 
+from synapse.util.caches.stream_change_cache import StreamChangeCache
+
 
 import logging
 
@@ -84,6 +85,7 @@ class DataStore(RoomMemberStore, RoomStore,
 
     def __init__(self, db_conn, hs):
         self.hs = hs
+        self.database_engine = hs.database_engine
 
         cur = db_conn.cursor()
         try:
@@ -117,8 +119,57 @@ class DataStore(RoomMemberStore, RoomStore,
         self._push_rule_id_gen = IdGenerator("push_rules", "id", self)
         self._push_rules_enable_id_gen = IdGenerator("push_rules_enable", "id", self)
 
+        events_max = self._stream_id_gen.get_max_token(None)
+        event_cache_prefill, min_event_val = self._get_cache_dict(
+            db_conn, "events",
+            entity_column="room_id",
+            stream_column="stream_ordering",
+            max_value=events_max,
+        )
+        self._events_stream_cache = StreamChangeCache(
+            "EventsRoomStreamChangeCache", min_event_val,
+            prefilled_cache=event_cache_prefill,
+        )
+
+        account_max = self._account_data_id_gen.get_max_token(None)
+        self._account_data_stream_cache = StreamChangeCache(
+            "AccountDataAndTagsChangeCache", account_max,
+        )
+
         super(DataStore, self).__init__(hs)
 
+    def _get_cache_dict(self, db_conn, table, entity_column, stream_column, max_value):
+        # Fetch a mapping of room_id -> max stream position for "recent" rooms.
+        # It doesn't really matter how many we get, the StreamChangeCache will
+        # do the right thing to ensure it respects the max size of cache.
+        sql = (
+            "SELECT %(entity)s, MAX(%(stream)s) FROM %(table)s"
+            " WHERE %(stream)s > ? - 100000"
+            " GROUP BY %(entity)s"
+        ) % {
+            "table": table,
+            "entity": entity_column,
+            "stream": stream_column,
+        }
+
+        sql = self.database_engine.convert_param_style(sql)
+
+        txn = db_conn.cursor()
+        txn.execute(sql, (int(max_value),))
+        rows = txn.fetchall()
+
+        cache = {
+            row[0]: int(row[1])
+            for row in rows
+        }
+
+        if cache:
+            min_val = min(cache.values())
+        else:
+            min_val = max_value
+
+        return cache, min_val
+
     @defer.inlineCallbacks
     def insert_client_ip(self, user, access_token, ip, user_agent):
         now = int(self._clock.time_msec())
diff --git a/synapse/storage/account_data.py b/synapse/storage/account_data.py
index ed6587429b..625d062eb1 100644
--- a/synapse/storage/account_data.py
+++ b/synapse/storage/account_data.py
@@ -14,7 +14,6 @@
 # limitations under the License.
 
 from ._base import SQLBaseStore
-from synapse.util.caches.stream_change_cache import StreamChangeCache
 from twisted.internet import defer
 
 import ujson as json
@@ -24,14 +23,6 @@ logger = logging.getLogger(__name__)
 
 
 class AccountDataStore(SQLBaseStore):
-    def __init__(self, hs):
-        super(AccountDataStore, self).__init__(hs)
-
-        self._account_data_stream_cache = StreamChangeCache(
-            "AccountDataAndTagsChangeCache",
-            self._account_data_id_gen.get_max_token(None),
-            max_size=10000,
-        )
 
     def get_account_data_for_user(self, user_id):
         """Get all the client account_data for a user.
diff --git a/synapse/storage/stream.py b/synapse/storage/stream.py
index 6e81d46c60..e245d2f914 100644
--- a/synapse/storage/stream.py
+++ b/synapse/storage/stream.py
@@ -37,7 +37,6 @@ from twisted.internet import defer
 
 from ._base import SQLBaseStore
 from synapse.util.caches.descriptors import cachedInlineCallbacks
-from synapse.util.caches.stream_change_cache import StreamChangeCache
 from synapse.api.constants import EventTypes
 from synapse.types import RoomStreamToken
 from synapse.util.logutils import log_function
@@ -78,13 +77,6 @@ def upper_bound(token):
 
 
 class StreamStore(SQLBaseStore):
-    def __init__(self, hs):
-        super(StreamStore, self).__init__(hs)
-
-        self._events_stream_cache = StreamChangeCache(
-            "EventsRoomStreamChangeCache", self._stream_id_gen.get_max_token(None)
-        )
-
     @defer.inlineCallbacks
     def get_appservice_room_stream(self, service, from_key, to_key, limit=0):
         # NB this lives here instead of appservice.py so we can reuse the