Thanks! I understand what was happening. I had tried MutableDict, but I think my data was too complex (a list-valued dictionary) for the basic implementation. When it didn't work I I got confused and thought reassigning the value would trigger mutation tracking.
On Tuesday, June 26, 2018 at 1:01:06 PM UTC-7, Mike Bayer wrote: > > On Tue, Jun 26, 2018 at 3:56 PM, Victor Reichert > <victor....@apptactoe.com <javascript:>> wrote: > > Hi, > > > > I have a class like: > > > > class SQLClass(db): > > > > json_field = Column(sqlalchemy.dialects.postgresql.JSONB) > > > > I'm doing something like: > > > > session.add( > > SQLClass(json_field = dict( > > key = [value1] > > ) > > )) > > > > session.commit() > > > > slq_class_obj = session.query(SQLClass).first() > > > > new_dict = slq_class_obj.json_field > > > > new_dict['key'].append(value2) > > > > slq_class_obj. json_field = new_dict > > > > print(slq_class_obj. json_field) # looks OK > > > > session.commt() > > > > print(slq_class_obj. json_field) # I just get [value1] > > > > The changes I made to json field (new_dict) were not persisted. > However, if > > just change the json_field to be an empty dict that is persisted. > > > > I know there are some issues with mutation and the JSON data type, but I > > thought since I was setting the field value rather than just mutating > the > > dict in place the mutation would be tracked. > > you are not creating a new dictionary above, just assigning the > attribute to itself. that's just in-place mutation. the attribute > system might log this as "changed" but when it goes to compare what it > loaded from the database with what the value is now, it will see they > are equal since they are the same object, and no net change. > > if your jsonb is storing just a dictionary, place mutabledict around > it and your problem is solved. > > http://docs.sqlalchemy.org/en/latest/orm/extensions/mutable.html?highlight=mutabledict#sqlalchemy.ext.mutable.MutableDict > > > > > > > > > > Why is setting the field to an empty dict persisted while my change is > not? > > Any general advice on handling JSON and mutation would also be welcome. > > > > Thank you for your help! > > > > ~Victor > > > > -- > > SQLAlchemy - > > The Python SQL Toolkit and Object Relational Mapper > > > > http://www.sqlalchemy.org/ > > > > To post example code, please provide an MCVE: Minimal, Complete, and > > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > > description. > > --- > > You received this message because you are subscribed to the Google > Groups > > "sqlalchemy" group. > > To unsubscribe from this group and stop receiving emails from it, send > an > > email to sqlalchemy+...@googlegroups.com <javascript:>. > > To post to this group, send email to sqlal...@googlegroups.com > <javascript:>. > > Visit this group at https://groups.google.com/group/sqlalchemy. > > For more options, visit https://groups.google.com/d/optout. > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
