From c10ac7806e2cde04f344b641d01efa46d34f9985 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Wed, 12 Aug 2015 17:16:30 +0100
Subject: [PATCH] Explain why we're prefilling dict with Nones
---
synapse/storage/state.py | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index a3fc859b06..57e334cc3e 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -412,6 +412,10 @@ class StateStore(SQLBaseStore):
for group, state_ids in group_state_dict.items():
if types:
+ # We delibrately put key -> None mappings into the cache to
+ # cache absence of the key, on the assumption that if we've
+ # explicitly asked for some types then we will probably ask
+ # for them again.
state_dict = {
key: None
for key in types
--
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