Fix 'no unique or exclusion constraint' error (#4591)

Add more tables to the list of tables which need a background update to
complete before we can upsert into them, which fixes a race against the
background updates.

changelog.d/4591.bugfix

@@ -0,0 +1 @@
+Fix 'no unique or exclusion constraint' error

synapse/storage/_base.py

@@ -50,6 +50,21 @@
 sql_txn_timer = Histogram("synapse_storage_transaction_time", "sec", ["desc"])
 
 
+# Unique indexes which have been added in background updates. Maps from table name
+# to the name of the background update which added the unique index to that table.
+#
+# This is used by the upsert logic to figure out which tables are safe to do a proper
+# UPSERT on: until the relevant background update has completed, we
+# have to emulate an upsert by locking the table.
+#
+UNIQUE_INDEX_BACKGROUND_UPDATES = {
+    "user_ips": "user_ips_device_unique_index",
+    "device_lists_remote_extremeties": "device_lists_remote_extremeties_unique_idx",
+    "device_lists_remote_cache": "device_lists_remote_cache_unique_idx",
+    "event_search": "event_search_event_id_idx",
+}
+
+
 class LoggingTransaction(object):
     """An object that almost-transparently proxies for the 'txn' object
     passed to the constructor. Adds logging and metrics to the .execute()
@@ -194,7 +209,7 @@ def __init__(self, db_conn, hs):
         self.database_engine = hs.database_engine
 
         # A set of tables that are not safe to use native upserts in.
-        self._unsafe_to_upsert_tables = {"user_ips"}
+        self._unsafe_to_upsert_tables = set(UNIQUE_INDEX_BACKGROUND_UPDATES.keys())
 
         # We add the user_directory_search table to the blacklist on SQLite
         # because the existing search table does not have an index, making it
@@ -230,12 +245,12 @@ def _check_safe_to_upsert(self):
         )
         updates = [x["update_name"] for x in updates]
 
-        # The User IPs table in schema #53 was missing a unique index, which we
-        # run as a background update.
-        if "user_ips_device_unique_index" not in updates:
-            self._unsafe_to_upsert_tables.discard("user_ips")
+        for table, update_name in UNIQUE_INDEX_BACKGROUND_UPDATES.items():
+            if update_name not in updates:
+                logger.debug("Now safe to upsert in %s", table)
+                self._unsafe_to_upsert_tables.discard(table)
 
-        # If there's any tables left to check, reschedule to run.
+        # If there's any updates still running, reschedule to run.
         if updates:
             self._clock.call_later(
                 15.0,