Require SQLite3 version 3.15 or above

This is primarily to allow tuple comparisons in queries, though a better
query optimiser and other improvements mean that using newer versions of
sqlite is highly recommended anyway.

synapse/storage/engines/__init__.py

@@ -15,7 +15,7 @@
 
 from ._base import IncorrectDatabaseSetup
 from .postgres import PostgresEngine
-from .sqlite3 import Sqlite3Engine
+from .sqlite3_engine import Sqlite3Engine
 
 import importlib
 import platform

synapse/storage/engines/sqlite3_engine.py

@@ -15,6 +15,7 @@
 
 from synapse.storage.prepare_database import prepare_database
 
+import sqlite3
 import struct
 import threading
 
@@ -25,6 +26,11 @@ class Sqlite3Engine(object):
     def __init__(self, database_module, database_config):
         self.module = database_module
 
+        if sqlite3.sqlite_version_info < (3, 15, 0):
+            raise RuntimeError(
+                "SQLite3 version is too old, Synapse requires 3.15 or later",
+            )
+
         # The current max state_group, or None if we haven't looked
         # in the DB yet.
         self._current_state_group_id = None