File 10719-Fix-instert-of-duplicate-key-into-event_json.patch of Package matrix-synapse

From d8917666d6198873bca140c3c511ae230ee698ec Mon Sep 17 00:00:00 2001
From: Jan Zerebecki <jan.suse@zerebecki.de>
Date: Mon, 30 Aug 2021 17:31:31 +0200
Subject: [PATCH] Fix instert of duplicate key into event_json

When an incoming event id is present in event_json but not in events
synapse fails trying to insert it with "psycopg2.errors.UniqueViolation:
duplicate key value violates unique constraints", because it is only
filtered based on those that are in events.

I don't know why those become out of sync, but this happening was
reported by others before.

Fix this by using an upsert (which inserts or updates existing records)
instead of a normal insert.

Please verify that this is the safe and correct thing to do before
merging this. Verify e.g. that it doesn't allow breaking history
integrity or something like it. As I don't know enough to understand
what this change entails.

Fixes: https://github.com/matrix-org/synapse/issues/10718
Signed-off-by: Jan Zerebecki <jan.suse@zerebecki.de>
---
 changelog.d/10719.bugfix                 |  1 +
 synapse/storage/databases/main/events.py | 22 +++++++++++-----------
 2 files changed, 12 insertions(+), 11 deletions(-)
 create mode 100644 changelog.d/10719.bugfix

diff --git a/changelog.d/10719.bugfix b/changelog.d/10719.bugfix
new file mode 100644
index 00000000000..d928f74f6bf
--- /dev/null
+++ b/changelog.d/10719.bugfix
@@ -0,0 +1 @@
+Fix instert failure because of duplicate key when an incoming event id is present in the table event_json but not in events.
diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index 40b53274fb3..830af72d5e6 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -1334,19 +1334,19 @@ def get_internal_metadata(event):
 
             return im
 
-        self.db_pool.simple_insert_many_txn(
+        self.db_pool.simple_upsert_many_txn(
             txn,
             table="event_json",
-            values=[
-                {
-                    "event_id": event.event_id,
-                    "room_id": event.room_id,
-                    "internal_metadata": json_encoder.encode(
-                        get_internal_metadata(event)
-                    ),
-                    "json": json_encoder.encode(event_dict(event)),
-                    "format_version": event.format_version,
-                }
+            key_names=["event_id"],
+            key_values=[[event.event_id] for event, _ in events_and_contexts],
+            value_names=["room_id", "internal_metadata", "json", "format_version"],
+            value_values=[
+                [
+                    event.room_id,
+                    json_encoder.encode(get_internal_metadata(event)),
+                    json_encoder.encode(event_dict(event)),
+                    event.format_version,
+                ]
                 for event, _ in events_and_contexts
             ],
         )