From 363565e6ac803c92786d46e29badfd342e4dfa76 Mon Sep 17 00:00:00 2001
From: "Olivier Wilkinson (reivilibre)" <oliverw@matrix.org>
Date: Tue, 21 Sep 2021 15:36:50 +0100
Subject: [PATCH] Add a stub implementation of `StateFilter.approx_difference`

---
 synapse/storage/state.py | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index 5e86befde4..806b0016d9 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -193,6 +193,14 @@ class StateFilter:
                 include_others=True,
             )
 
+    def approx_difference(self, subtrahend: "StateFilter") -> "StateFilter":
+        """
+        Stub implementation! Satisfies the condition that it's an overestimate.
+        """
+        if self == subtrahend:
+            return StateFilter.none()
+        return self
+
     def make_sql_filter_clause(self) -> Tuple[str, List[str]]:
         """Converts the filter to an SQL clause.