Engine AC doesn't contain start/close_connection_pool() method.

[gmos]

@app.on_event("startup")
async def open_database_connection_pool():
    engine = engine_finder()
    await engine.start_connection_pool()


@app.on_event("shutdown")
async def close_database_connection_pool():
    engine = engine_finder()
    await engine.close_connection_pool()

This code is in many of the sample applications. The engine_finder() is typed as Engine, which is an abstract class. It doesn't however provide an (@abstract)method for start_connection_pool() and close_connection_pool(). These methods only exist in the concrete subclass for Postgres. Hence vscode/pylance complain about non-existing methods.

I can do a PR, but am unsure about best solution.
Personally I would add these methods as normal methods to the Engine class, just providing a colored_warning() that pooling is not implemented for the provided engine.

Alternatively all sample programs using the connection pool could be changed like:

@app.on_event("startup")
async def open_database_connection_pool():
    engine = engine_finder()
    if isinstance(engine, PostgresEngine):
        await engine.start_connection_pool()

[dantownsend]

@gmos You're right, this could be improved.

Adding a method to Engine is a good idea. As you say, it can just output a warning, and should be overridden in child classes.

Even with that change, Pylance might still complain because engine_finder can potentially return None. So the example code should be like you suggested:

@app.on_event("startup")
async def open_database_connection_pool():
    engine = engine_finder()
    if isinstance(engine, PostgresEngine):
        await engine.start_connection_pool()

If you're happy to do a PR, that would be great.