SQLAlchemy default filter

Question

I have a model with a field is_deleted, now I want all forms of query for this model to always filter by is_deleted=False in addition to whatever filtering arguments is passed to .filter and .filter_by.

In Django, I would normally override the manager and add my own filtering but I need help for SQLAlchemy.

UPDATE:

I ended-up doing the following:

class CustomQuery(Query):     def __new__(cls, *args, **kwargs):         if args and hasattr(args[0][0], "is_deleted"):             return Query(*args, **kwargs).filter_by(is_deleted=False)         else:             return object.__new__(cls) session = scoped_session(sessionmaker(query_cls=CustomQuery)) 

It works but if I have more fields later on I imagine I'll have to add more condition, there must be a way to do this on the model level.

Answer 1

This is a very old question so I'm sure the OP solved their issue, but as it remains unanswered (in 2021) here's how we've approached applying a custom query class to all models:

1. Define the custom query as above

class CustomQuery(Query): ... 

2. Then set this query class as the query attribute on your base model class:

class BaseModel(Model):     __abstract__ = True     query_class = CustomQuery     ... 

Then any models implementing the BaseModel will obviously inherit this behaviour:

class MyModel(BaseModel):     __tablename__ = 'my_model'      ....  

Note, in our case not all of the tables follow the soft delete pattern (we don't care about the history of every single table). Here, you could implement a separate BaseModel that uses the default query class.

class ImmutableBaseModel(Model):     __abstract__ = True     query_class = CustomQuery     ...  class MutableBaseModel(Model):     __abstract__ = True  

If you find yourself here and you've not read it yet check out this excellent blog post from Miguel Grinberg on implementing the soft delete pattern and accompanying repo