7 files changed, 14 insertions, 87 deletions
diff --git a/synapse/storage/database.py b/synapse/storage/database.py
index 94590e7b45..b302cd5786 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -2059,69 +2059,18 @@ def make_in_list_sql_clause(
 KV = TypeVar("KV")
 
 
-def make_tuple_comparison_clause(
-    database_engine: BaseDatabaseEngine, keys: List[Tuple[str, KV]]
-) -> Tuple[str, List[KV]]:
+def make_tuple_comparison_clause(keys: List[Tuple[str, KV]]) -> Tuple[str, List[KV]]:
     """Returns a tuple comparison SQL clause
 
-    Depending what the SQL engine supports, builds a SQL clause that looks like either
-    "(a, b) > (?, ?)", or "(a > ?) OR (a == ? AND b > ?)".
+    Builds a SQL clause that looks like "(a, b) > (?, ?)"
 
     Args:
-        database_engine
         keys: A set of (column, value) pairs to be compared.
 
     Returns:
         A tuple of SQL query and the args
     """
-    if database_engine.supports_tuple_comparison:
-        return (
-            "(%s) > (%s)" % (",".join(k[0] for k in keys), ",".join("?" for _ in keys)),
-            [k[1] for k in keys],
-        )
-
-    # we want to build a clause
-    #    (a > ?) OR
-    #    (a == ? AND b > ?) OR
-    #    (a == ? AND b == ? AND c > ?)
-    #    ...
-    #    (a == ? AND b == ? AND ... AND z > ?)
-    #
-    # or, equivalently:
-    #
-    #  (a > ? OR (a == ? AND
-    #    (b > ? OR (b == ? AND
-    #      ...
-    #        (y > ? OR (y == ? AND
-    #          z > ?
-    #        ))
-    #      ...
-    #    ))
-    #  ))
-    #
-    # which itself is equivalent to (and apparently easier for the query optimiser):
-    #
-    #  (a >= ? AND (a > ? OR
-    #    (b >= ? AND (b > ? OR
-    #      ...
-    #        (y >= ? AND (y > ? OR
-    #          z > ?
-    #        ))
-    #      ...
-    #    ))
-    #  ))
-    #
-    #
-
-    clause = ""
-    args = []  # type: List[KV]
-    for k, v in keys[:-1]:
-        clause = clause + "(%s >= ? AND (%s > ? OR " % (k, k)
-        args.extend([v, v])
-
-    (k, v) = keys[-1]
-    clause += "%s > ?" % (k,)
-    args.append(v)
-
-    clause += "))" * (len(keys) - 1)
-    return clause, args
+    return (
+        "(%s) > (%s)" % (",".join(k[0] for k in keys), ",".join("?" for _ in keys)),
+        [k[1] for k in keys],
+    )
diff --git a/synapse/storage/databases/main/client_ips.py b/synapse/storage/databases/main/client_ips.py
index 6d18e692b0..ea3c15fd0e 100644
--- a/synapse/storage/databases/main/client_ips.py
+++ b/synapse/storage/databases/main/client_ips.py
@@ -298,7 +298,6 @@ class ClientIpBackgroundUpdateStore(SQLBaseStore):
             #      times, which is fine.
 
             where_clause, where_args = make_tuple_comparison_clause(
-                self.database_engine,
                 [("user_id", last_user_id), ("device_id", last_device_id)],
             )
 
diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index d327e9aa0b..9bf8ba888f 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -985,7 +985,7 @@ class DeviceBackgroundUpdateStore(SQLBaseStore):
 
         def _txn(txn):
             clause, args = make_tuple_comparison_clause(
-                self.db_pool.engine, [(x, last_row[x]) for x in KEY_COLS]
+                [(x, last_row[x]) for x in KEY_COLS]
             )
             sql = """
                 SELECT stream_id, destination, user_id, device_id, MAX(ts) AS ts
diff --git a/synapse/storage/databases/main/events_bg_updates.py b/synapse/storage/databases/main/events_bg_updates.py
index 78367ea58d..79e7df6ca9 100644
--- a/synapse/storage/databases/main/events_bg_updates.py
+++ b/synapse/storage/databases/main/events_bg_updates.py
@@ -838,7 +838,6 @@ class EventsBackgroundUpdatesStore(SQLBaseStore):
         # We want to do a `(topological_ordering, stream_ordering) > (?,?)`
         # comparison, but that is not supported on older SQLite versions
         tuple_clause, tuple_args = make_tuple_comparison_clause(
-            self.database_engine,
             [
                 ("events.room_id", last_room_id),
                 ("topological_ordering", last_depth),
diff --git a/synapse/storage/engines/_base.py b/synapse/storage/engines/_base.py
index cca839c70f..21db1645d3 100644
--- a/synapse/storage/engines/_base.py
+++ b/synapse/storage/engines/_base.py
@@ -44,14 +44,6 @@ class BaseDatabaseEngine(Generic[ConnectionType], metaclass=abc.ABCMeta):
 
     @property
     @abc.abstractmethod
-    def supports_tuple_comparison(self) -> bool:
-        """
-        Do we support comparing tuples, i.e. `(a, b) > (c, d)`?
-        """
-        ...
-
-    @property
-    @abc.abstractmethod
     def supports_using_any_list(self) -> bool:
         """
         Do we support using `a = ANY(?)` and passing a list
diff --git a/synapse/storage/engines/postgres.py b/synapse/storage/engines/postgres.py
index 80a3558aec..dba8cc51d3 100644
--- a/synapse/storage/engines/postgres.py
+++ b/synapse/storage/engines/postgres.py
@@ -47,8 +47,8 @@ class PostgresEngine(BaseDatabaseEngine):
         self._version = db_conn.server_version
 
         # Are we on a supported PostgreSQL version?
-        if not allow_outdated_version and self._version < 90500:
-            raise RuntimeError("Synapse requires PostgreSQL 9.5+ or above.")
+        if not allow_outdated_version and self._version < 90600:
+            raise RuntimeError("Synapse requires PostgreSQL 9.6 or above.")
 
         with db_conn.cursor() as txn:
             txn.execute("SHOW SERVER_ENCODING")
@@ -130,13 +130,6 @@ class PostgresEngine(BaseDatabaseEngine):
         return True
 
     @property
-    def supports_tuple_comparison(self):
-        """
-        Do we support comparing tuples, i.e. `(a, b) > (c, d)`?
-        """
-        return True
-
-    @property
     def supports_using_any_list(self):
         """Do we support using `a = ANY(?)` and passing a list"""
         return True
diff --git a/synapse/storage/engines/sqlite.py b/synapse/storage/engines/sqlite.py
index b87e7798da..f4f16456f2 100644
--- a/synapse/storage/engines/sqlite.py
+++ b/synapse/storage/engines/sqlite.py
@@ -57,14 +57,6 @@ class Sqlite3Engine(BaseDatabaseEngine["sqlite3.Connection"]):
         return self.module.sqlite_version_info >= (3, 24, 0)
 
     @property
-    def supports_tuple_comparison(self):
-        """
-        Do we support comparing tuples, i.e. `(a, b) > (c, d)`? This requires
-        SQLite 3.15+.
-        """
-        return self.module.sqlite_version_info >= (3, 15, 0)
-
-    @property
     def supports_using_any_list(self):
         """Do we support using `a = ANY(?)` and passing a list"""
         return False
@@ -72,8 +64,11 @@ class Sqlite3Engine(BaseDatabaseEngine["sqlite3.Connection"]):
     def check_database(self, db_conn, allow_outdated_version: bool = False):
         if not allow_outdated_version:
             version = self.module.sqlite_version_info
-            if version < (3, 11, 0):
-                raise RuntimeError("Synapse requires sqlite 3.11 or above.")
+            # Synapse is untested against older SQLite versions, and we don't want
+            # to let users upgrade to a version of Synapse with broken support for their
+            # sqlite version, because it risks leaving them with a half-upgraded db.
+            if version < (3, 22, 0):
+                raise RuntimeError("Synapse requires sqlite 3.22 or above.")
 
     def check_new_database(self, txn):
         """Gets called when setting up a brand new database. This allows us to