Store URL cache preview downloads seperately

This makes it easier to clear old media out at a later date

synapse/storage/media_repository.py

@@ -30,13 +30,16 @@ class MediaRepositoryStore(SQLBaseStore):
         return self._simple_select_one(
             "local_media_repository",
             {"media_id": media_id},
-            ("media_type", "media_length", "upload_name", "created_ts", "quarantined_by"),
+            (
+                "media_type", "media_length", "upload_name", "created_ts",
+                "quarantined_by", "url_cache",
+            ),
             allow_none=True,
             desc="get_local_media",
         )
 
     def store_local_media(self, media_id, media_type, time_now_ms, upload_name,
-                          media_length, user_id):
+                          media_length, user_id, url_cache=None):
         return self._simple_insert(
             "local_media_repository",
             {
@@ -46,6 +49,7 @@ class MediaRepositoryStore(SQLBaseStore):
                 "upload_name": upload_name,
                 "media_length": media_length,
                 "user_id": user_id.to_string(),
+                "url_cache": url_cache,
             },
             desc="store_local_media",
         )

synapse/storage/schema/delta/43/url_cache.sql

@@ -0,0 +1,16 @@
+/* Copyright 2017 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.
+ */
+
+ALTER TABLE local_media_repository ADD COLUMN url_cache TEXT;