Incorporate review

2 files changed, 7 insertions, 1 deletions

diff --git a/synapse/storage/data_stores/main/events.py b/synapse/storage/data_stores/main/events.py
index 577e79bcf9..1045c7fa2e 100644
--- a/synapse/storage/data_stores/main/events.py
+++ b/synapse/storage/data_stores/main/events.py
@@ -1491,7 +1491,7 @@ class EventsStore(
             self._handle_event_relations(txn, event)
 
             # Store the labels for this event.
-            labels = event.content.get(EventContentFields.Labels)
+            labels = event.content.get(EventContentFields.LABELS)
             if labels:
                 self.insert_labels_for_event_txn(
                     txn, event.event_id, labels, event.room_id, event.depth
diff --git a/synapse/storage/data_stores/main/schema/delta/56/event_labels.sql b/synapse/storage/data_stores/main/schema/delta/56/event_labels.sql
index 2acd8e1be5..5e29c1da19 100644
--- a/synapse/storage/data_stores/main/schema/delta/56/event_labels.sql
+++ b/synapse/storage/data_stores/main/schema/delta/56/event_labels.sql
@@ -13,6 +13,8 @@
  * limitations under the License.
  */
 
+-- room_id and topoligical_ordering are denormalised from the events table in order to
+-- make the index work.
 CREATE TABLE IF NOT EXISTS event_labels (
     event_id TEXT,
     label TEXT,
@@ -21,4 +23,8 @@ CREATE TABLE IF NOT EXISTS event_labels (
     PRIMARY KEY(event_id, label)
 );
 
+
+-- This index enables an event pagination looking for a particular label to index the
+-- event_labels table first, which is much quicker than scanning the events table and then
+-- filtering by label, if the label is rarely used relative to the size of the room.
 CREATE INDEX event_labels_room_id_label_idx ON event_labels(room_id, label, topological_ordering);