Test some ideas that might help performance a bit

synapse/storage/_base.py

@@ -440,14 +440,29 @@ class SQLBaseStore(object):
         )
 
     def _get_events_txn(self, txn, event_ids):
-        events = []
-        for e_id in event_ids:
-            ev = self._get_event_txn(txn, e_id)
+	if not event_ids:
+		return []
 
-            if ev:
-                events.append(ev)
+	if len(event_ids) > 50:
+		events = []
+		n = 50
+		for e_ids in [event_ids[i:i + n] for i in range(0, len(event_ids), n)]:
+			events.extend(self._get_events_txn(txn, e_ids))
+		return events
 
-        return events
+        where_clause = " OR ".join(["e.event_id = ?" for _ in event_ids])
+
+        sql = (
+            "SELECT internal_metadata, json, r.event_id FROM event_json as e "
+            "LEFT JOIN redactions as r ON e.event_id = r.redacts "
+            "WHERE %s"
+        ) % (where_clause,)
+
+        txn.execute(sql, event_ids)
+
+        res = txn.fetchall()
+
+        return [self._get_event_from_row_txn(txn, *r) for r in res]
 
     def _get_event_txn(self, txn, event_id, check_redacted=True,
                        get_prev_content=True):
@@ -467,6 +482,13 @@ class SQLBaseStore(object):
 
         internal_metadata, js, redacted = res
 
+	return self._get_event_from_row_txn(
+		txn, internal_metadata, js, redacted, check_redacted=check_redacted,
+		get_prev_content=get_prev_content,
+	)
+
+    def _get_event_from_row_txn(self, txn, internal_metadata, js, redacted,
+				check_redacted=True, get_prev_content=True):
         d = json.loads(js)
         internal_metadata = json.loads(internal_metadata)