From 5ea26508e072f684b70fce02529847499822830d Mon Sep 17 00:00:00 2001
From: Patrick Cloke <patrickc@matrix.org>
Date: Tue, 7 Nov 2023 09:20:56 -0500
Subject: [PATCH 1/2] Avoid updating the same rows multiple times.

---
 synapse/storage/database.py | 5 +----
 tests/storage/test_base.py  | 4 ++--
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/synapse/storage/database.py b/synapse/storage/database.py
index abc7d8a5d268..302f82342202 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -2047,10 +2047,7 @@ def simple_update_many_txn(
 
         # List of tuples of (value values, then key values)
         # (This matches the order needed for the query)
-        args = [tuple(x) + tuple(y) for x, y in zip(value_values, key_values)]
-
-        for ks, vs in zip(key_values, value_values):
-            args.append(tuple(vs) + tuple(ks))
+        args = [tuple(vv) + tuple(kv) for vv, kv in zip(value_values, key_values)]
 
         # 'col1 = ?, col2 = ?, ...'
         set_clause = ", ".join(f"{n} = ?" for n in value_names)
diff --git a/tests/storage/test_base.py b/tests/storage/test_base.py
index b4c490b568f2..5bae1b67bfd5 100644
--- a/tests/storage/test_base.py
+++ b/tests/storage/test_base.py
@@ -371,12 +371,12 @@ def test_update_many(self) -> Generator["defer.Deferred[object]", object, None]:
             self.mock_execute_batch.assert_called_once_with(
                 self.mock_txn,
                 "UPDATE tablename SET col3 = ? WHERE col1 = ? AND col2 = ?",
-                [("val3", "val1", "val2"), ("val3", "val1", "val2")],
+                [("val3", "val1", "val2")],
             )
         else:
             self.mock_txn.executemany.assert_called_once_with(
                 "UPDATE tablename SET col3 = ? WHERE col1 = ? AND col2 = ?",
-                [("val3", "val1", "val2"), ("val3", "val1", "val2")],
+                [("val3", "val1", "val2")],
             )
 
         # key_values and value_values must be the same length.

From 5dd32b24060804cb4dafb41b9425a9e55e70675d Mon Sep 17 00:00:00 2001
From: Patrick Cloke <patrickc@matrix.org>
Date: Tue, 7 Nov 2023 12:55:47 -0500
Subject: [PATCH 2/2] Newsfragment

---
 changelog.d/16609.bugfix | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/16609.bugfix

diff --git a/changelog.d/16609.bugfix b/changelog.d/16609.bugfix
new file mode 100644
index 000000000000..a52d395cd332
--- /dev/null
+++ b/changelog.d/16609.bugfix
@@ -0,0 +1 @@
+Fix a long-standing bug where some queries updated the same row twice. Introduced in Synapse 1.57.0.