From 6ba21bf2b8207e714d0d523379727bcf2c14684d Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Wed, 7 Jun 2017 11:08:36 +0100
Subject: [PATCH] Comments

---
 synapse/storage/roommember.py | 9 +++++++++
 synapse/storage/state.py      | 6 ++++++
 2 files changed, 15 insertions(+)

diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index 7155bfdc69..8656455f6e 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -644,6 +644,10 @@ class RoomMemberStore(SQLBaseStore):
 
 
 class _JoinedHostsCache(object):
+    """Cache for joined hosts in a room that is optimised to handle updates
+    via state deltas.
+    """
+
     def __init__(self, store, room_id):
         self.store = store
         self.room_id = room_id
@@ -658,6 +662,11 @@ class _JoinedHostsCache(object):
 
     @defer.inlineCallbacks
     def get_destinations(self, state_entry):
+        """Get set of destinations for a state entry
+
+        Args:
+            state_entry(synapse.state._StateCacheEntry)
+        """
         if state_entry.state_group == self.state_group:
             defer.returnValue(frozenset(self.hosts_to_joined_users))
 
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index 01474ff5ff..c3eecbe824 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -99,6 +99,12 @@ class StateStore(SQLBaseStore):
         )
 
     def get_state_group_delta(self, state_group):
+        """Given a state group try to return a previous group and a delta between
+        the old and the new.
+
+        Returns:
+            (prev_group, delta_ids), where both may be None.
+        """
         def _get_state_group_delta_txn(txn):
             prev_group = self._simple_select_one_onecol_txn(
                 txn,