Add an API for listing threads in a room. (#13394)

Implement the /threads endpoint from MSC3856.

This is currently unstable and behind an experimental configuration
flag.

It includes a background update to backfill data, results from
the /threads endpoint will be partial until that finishes.

1 files changed, 30 insertions, 0 deletions

diff --git a/synapse/storage/schema/main/delta/73/09threads_table.sql b/synapse/storage/schema/main/delta/73/09threads_table.sql
new file mode 100644
index 0000000000..aa7c5e9a2e
--- /dev/null
+++ b/synapse/storage/schema/main/delta/73/09threads_table.sql
@@ -0,0 +1,30 @@
+/* Copyright 2022 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.
+ */
+
+CREATE TABLE threads (
+    room_id TEXT NOT NULL,
+    -- The event ID of the root event in the thread.
+    thread_id TEXT NOT NULL,
+    -- The latest event ID and corresponding topo / stream ordering.
+    latest_event_id TEXT NOT NULL,
+    topological_ordering BIGINT NOT NULL,
+    stream_ordering BIGINT NOT NULL,
+    CONSTRAINT threads_uniqueness UNIQUE (room_id, thread_id)
+);
+
+CREATE INDEX threads_ordering_idx ON threads(room_id, topological_ordering, stream_ordering);
+
+INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+  (7309, 'threads_backfill', '{}');