SQLAlchemy models attribute operations and DB access

Question

Let's say that I have SQLAlchemy ORM model instance model and name of it's attribute attr_name.

Is there a way to determine whether getattr(model, attr_name) will or won't query the database? I mean that I need a function getattr_does_emit_sql(model, attr_name) returning True or False.

Hmm. Are you asking if it can be determined programmatically, at runtime, or manually (by debugging and inspecting models objects, logging, etc..)? — Lukas Graf
– Lukas Graf, Commented Nov 20, 2013 at 11:44

Bartosz Marcinkowski · Accepted Answer · 2013-11-20 14:50:08Z

1

Solved it. The function is

from sqlalchemy.orm.attributes import QueryableAttribute
def getattr_does_emit_sql(model, attr_name):
    return (attr_name not in model.__dict__ 
        and hasattr(type(model), attr_name
        and isinstance(getattr(type(model), attr_name), QueryableAttribute)
    )

answered Nov 20, 2013 at 14:50

Bartosz Marcinkowski

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