sanity check that config db_url and async_db_url are the same

throw a warning if the part following the `://` differs between these two

reflex/config.py

@@ -625,7 +625,7 @@ class Config(Base):
     db_url: Optional[str] = "sqlite:///reflex.db"
 
     # The async database url used by rx.Model.
-    async_db_url: Optional[str] = "sqlite+aiosqlite:///reflex.db"
+    async_db_url: Optional[str] = None
 
     # The redis url
     redis_url: Optional[str] = None

reflex/model.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import re
 from collections import defaultdict
 from typing import Any, ClassVar, Optional, Type, Union
 
@@ -26,6 +27,21 @@ _ENGINE: dict[str, sqlalchemy.engine.Engine] = {}
 _ASYNC_ENGINE: dict[str, sqlalchemy.engine.Engine] = {}
 _AsyncSessionLocal: dict[str | None, sqlalchemy.orm.sessionmaker] = {}
 
+# Import asyncio session _after_ reflex.utils.compat
+import sqlmodel.ext.asyncio.session  # noqa: E402
+
+
+def _safe_db_url_for_logging(url: str) -> str:
+    """Remove username and password from the database URL for logging.
+
+    Args:
+        url: The database URL.
+
+    Returns:
+        The database URL with the username and password removed.
+    """
+    return re.sub(r"://[^@]+@", "://<username>:<password>@", url)
+
 
 def get_engine_args(url: str | None = None) -> dict[str, Any]:
     """Get the database engine arguments.
@@ -94,8 +110,18 @@ def get_async_engine(url: str | None) -> sqlalchemy.engine.Engine:
     Raises:
         ValueError: If the async database url is None.
     """
-    conf = get_config()
+    if url is None:
-    url = url or conf.async_db_url
+        conf = get_config()
+        url = conf.async_db_url
+        if url is not None and conf.db_url is not None:
+            async_db_url_tail = url.partition("://")[2]
+            db_url_tail = conf.db_url.partition("://")[2]
+            if async_db_url_tail != db_url_tail:
+                console.warn(
+                    f"async_db_url `{_safe_db_url_for_logging(url)}` "
+                    "should reference the same database as "
+                    f"db_url `{_safe_db_url_for_logging(conf.db_url)}`."
+                )
     if url is None:
         raise ValueError("No async database url configured")