What is the best way to change out the primary key of a database? Probably making another database and export/import? I don't wanna do it manually, would it work to specify two different versions of the database and copy the data in python?

primary key of a table?

looks like len(Entity.select()) works, is this a fine way of doing it?

any of this: select(count() for x in MyObject).get() get(count() for x in MyObject) MyObject.select().count() also possible: select(count(x) for x in MyObject).get() get(count(x) for x in MyObject)

https://editor.ponyorm.com/user/luckydonald/Tags The `Sticker` table has a `file_id` column, which is PK. Problem is, Telegram recent changed the way the file IDs are calculated. So I am required to change 'em all. Problem is many tables are referring it. I think the best would to replace it with a Auto increment PK, in case there are future changes.

I think this case is too hard for migrations, because change of primary key is a very seldom operation and requires complex cascade actions. I suggest you to have two different files with definition of models, connect to both databases and copy objects from one database to another

looks like len(Entity.select()) works, is this a fine way of doing it?

Regarding counting the number of objects, actually the shortest form is: orm.count(x for x in MyObject)

select count(*) from table1

In all databases

Instead of obj.to_dict(obj) you need to write just obj.to_dict()

How does Pony handle float/double?

Pony represents float/double database type as float type in Python (which actually has double precision). The type of a database column which Pony creates is DOUBLE PRECISION. You can specify sql_type='real' if you want to create a column with a single precision

Well... you asked about get, and select is entirely different story. Pony should translate select generator code to SQL, and cannot translate your function, because it doesn't know what equivalent SQL should be. I don't know it too :) Also, the function that you wrote expects keyword arguments, not positional ones as you use inside the query. 1) I suggest you to write selects explicitly: games = select(g for g in Game if (g.name == name or name is None) and (g.version == version or version is None)) 2) You can also build query incrementally: query = select(g for g in Game) if name is not None: query = query.filter(lambda g: g.name == name) if version is not None: query = query.filter(lambda g: g.version == version) 3) Probably even something like that should work: def ignore_none(query, **kwargs): for key, value in kwargs.items(): if value is not None: query = query.filter(lambda x: getattr(x, key) == value) return query query = select(g for g in Game) query = ignore_none(query, name='X', version='Y') I didn't test it. Theoretically it should work, but there is an open issue 223, which describes a bug with getattr which is not fixed yet. You may follow approach (2) for safety

page_size = 1000 page_num = 1 while True: with db_session: objects = MyObject.select(). \ order_by(MyObject.id). \ page(page_num, page_size) process_objects(objects) if len(objects) < page_size: break page_num += 1

So with yield from objects it does, and I can't do that. Thanks.

Hello! Why pony do lazy load for queries like: select((x, y) for x in X for y in Y if x.key1 == y.key2)

In most cases PyCharm works good

Is it possible preload all attrs?

Does pony automatically creates new Tables if I add a db.Entity, and use db.generate_mapping(create_tables=True), even if there already are Tables?