CODEWITHSUNDEEP
pythonmysqlpython-2.7sqlalchemypyramid
Chris W.
Chris W.

Reputation: 39239

Detect if a SQLAlchemy model has pending write operations associated with it

I have an application in which I query against a SQL database and end up with a SQL Alchemy object representing a given row. Then, based on user input and a series of if/then statements I may perform an update on the SQLA object.

i.e., 

if 'fooinput1' in payload:
   sqla_instance.foo1 = validate_foo1(fooinput1)
if 'fooinput2' in payload:
   sqla_instance.foo2 = validate_foo2(fooinput2)
...

I now need to add modified_at and modified_by data to this system. Is it possible to check something on the SQLA instance like sqla_instance.was_modified or sqla_instance.update_pending to determine if a modification was performed?

(I recognize that I could maintain my own was_modified boolean, but since there are many of these if/then clauses that would lead to a lot of boilerplate which I'd like to avoid if possible.)

FWIW: this is a python 2.7 pyramids app reading from a MySQL db in the context of a web request.

Upvotes: 2

Views: 1350

Answers (3)

Sergey
Sergey

Reputation: 12427

Depending on the number of fields which modification you want to track you may achieve what you need using ORM Events:

@sa.event.listens_for(Thing.foo, 'set')
def foo_changed(target, value, oldvalue, initiator):
    target.last_modified = datetime.now()

@sa.event.listens_for(Thing.baz, 'set')
def baz_changed(target, value, oldvalue, initiator):
    target.last_modified = datetime.now()

Upvotes: 1

RAJAHMAD MULANI
RAJAHMAD MULANI

Reputation: 184

The session object provides events, which may help you. just review once, -->Transient to pending status for session object

Upvotes: 0

badger0053
badger0053

Reputation: 1209

The Session object SQL Alchemy ORM provides has two attributes that can help with what you are trying to do:

1) Session.is_modified()

2) Session.dirty

Upvotes: 3

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