improve migration implementation

py/alembic.ini

@@ -1,6 +1,6 @@
 [alembic]
 script_location = migrations
-sqlalchemy.url = postgresql+asyncpg://postgres:postgres@localhost/postgres
+sqlalchemy.url = postgresql://postgres:postgres@localhost:5432/postgres
 
 [loggers]
 keys = root,sqlalchemy,alembic
@@ -34,4 +34,4 @@ formatter = generic
 
 [formatter_generic]
 format = %(levelname)-5.5s [%(name)s] %(message)s
-datefmt = %H:%M:%S
+datefmt = %H:%M:%

py/migrations/env.py

@@ -1,23 +1,41 @@
-import asyncio
 from logging.config import fileConfig
 
-from sqlalchemy import pool
-from sqlalchemy.engine import Connection
-from sqlalchemy.ext.asyncio import async_engine_from_config
-
 from alembic import context
+from sqlalchemy import engine_from_config, pool
 
-# Import your models/metadata
-from your_project.models import Base
-
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
 config = context.config
-target_metadata = Base.metadata
 
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
 if config.config_file_name is not None:
     fileConfig(config.config_file_name)
 
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+target_metadata = None
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
 def run_migrations_offline() -> None:
-    """Run migrations in 'offline' mode."""
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
     url = config.get_main_option("sqlalchemy.url")
     context.configure(
         url=url,
@@ -29,26 +47,28 @@ def run_migrations_offline() -> None:
     with context.begin_transaction():
         context.run_migrations()
 
-def do_run_migrations(connection: Connection) -> None:
-    context.configure(connection=connection, target_metadata=target_metadata)
-    with context.begin_transaction():
-        context.run_migrations()
 
-async def run_async_migrations() -> None:
-    connectable = async_engine_from_config(
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
         config.get_section(config.config_ini_section, {}),
         prefix="sqlalchemy.",
         poolclass=pool.NullPool,
     )
 
-    async with connectable.connect() as connection:
-        await connection.run_sync(do_run_migrations)
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection, target_metadata=target_metadata
+        )
 
-    await connectable.dispose()
+        with context.begin_transaction():
+            context.run_migrations()
 
-def run_migrations_online() -> None:
-    """Run migrations in 'online' mode."""
-    asyncio.run(run_async_migrations())
 
 if context.is_offline_mode():
     run_migrations_offline()

py/migrations/script.py.mako

@@ -11,7 +11,7 @@ from alembic import op
 import sqlalchemy as sa
 ${imports if imports else ""}
 
-# revision identifiers, used by Alembic
+# revision identifiers, used by Alembic.
 revision: str = ${repr(up_revision)}
 down_revision: Union[str, None] = ${repr(down_revision)}
 branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}