text: from logging.config import fileConfig
  import os
  from sqlalchemy import engine_from_config
  from sqlalchemy import pool
  from alembic import context
  from app.db.base import Base
  
  # this is the Alembic Config object, which provides
  # access to the values within the .ini file in use.
  config = context.config
  
  # Interpret the config file for Python logging.
  # This line sets up loggers basically.
  fileConfig(config.config_file_name)
  
  # add your model's MetaData object here
  # for 'autogenerate' support
  target_metadata = Base.metadata
  # target_metadata = None
  
  
  def get_url():
    user = os.getenv("POSTGRES_USER", "postgres")
    password = os.getenv("POSTGRES_PASSWORD", "")
    server = os.getenv("POSTGRES_SERVER", "db")
    port = os.getenv("POSTGRES_PORT", "5432")
    db = os.getenv("POSTGRES_DB", "app")
    return f"postgresql://{user}:{password}@{server}:{port}/{db}"
  
  
  # 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():
    """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")
    url = get_url()
    context.configure(
      url=url,
      target_metadata=target_metadata,
      literal_binds=True,
      dialect_opts={"paramstyle": "named"},
    )
  
    with context.begin_transaction():
      context.run_migrations()
  
  
  def run_migrations_online():
    """Run migrations in 'online' mode.
  
      In this scenario we need to create an Engine
      and associate a connection with the context.
  
      """
    configuration = config.get_section(config.config_ini_section)
    configuration["sqlalchemy.url"] = get_url()
    connectable = engine_from_config(
      configuration,
      prefix="sqlalchemy.",
      poolclass=pool.NullPool,
    )
  
    with connectable.connect() as connection:
      context.configure(connection=connection, target_metadata=target_metadata)
  
      with context.begin_transaction():
        context.run_migrations()
  
  
  if context.is_offline_mode():
    run_migrations_offline()
  else:
    run_migrations_online()
  