Re: [sqlalchemy] Re: Wierdness with JSONB / Python dictionary
And, for that matter, the trouble I was having should have warned me about my data structure - I need to use an association table, not bury data in a JSONB column. Thanks again. -- 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.
Re: [sqlalchemy] Re: Wierdness with JSONB / Python dictionary
It helps a great deal, thank you Simon. Thanks for taking the time to explain it for me. -- 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.
Re: [sqlalchemy] Re: Wierdness with JSONB / Python dictionary
On Wed, Jun 28, 2017 at 1:35 AM, Andrew Mwrote: > I can also replicate it with JSON, with a table defined as follows: > > class Test(Base): > __tablename__ = 'test' > id = Column(INT, primary_key=True, index=True) > json = Column(JSON, default={}) > > And running the following code: > > p0 = Test() > p1 = Test() > session.add(p0) > session.add(p1) > session.commit() > p0.json # {} > p1.json # {} > > p0.json['US'] = 999 > p1.json = {'US': 999} > p0.json == p1.json # True > > session.commit() > p0.json # {} > p1.json # {'US': 999} > p0.json == p1.json # False > > I'm running the latest version of SQLAlchemy (1.1.11 on Python 3.6). Any > thoughts, please? > > Thanks, > Andrew When SQLAlchemy creates a property that corresponds to a column in a table, it sets up event listeners that are triggered whenever that property is assigned to. The event listeners tell the SQLAlchemy session that the object has been modified, so SA can send the changes to the database on the next flush. With JSON columns, the value is typically a mutable structure (a list or a dict). They are the native Python types, so there is no mechanism for SA to be notified when some entry in that structure changes. Since SA doesn't see the change, it doesn't consider the object to be modified, so the changes don't get flushed. The fix is to not use a native Python dict for the property value, but instead to use something that will notify SA when its contents change. SA has an extension that provides MutableDict and MutableList classes, as well as tools to build your own more specialized types: http://docs.sqlalchemy.org/en/latest/orm/extensions/mutable.html Hope that helps, Simon -- 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.
[sqlalchemy] Re: Wierdness with JSONB / Python dictionary
I can also replicate it with JSON, with a table defined as follows: class Test(Base): __tablename__ = 'test' id = Column(INT, primary_key=True, index=True) json = Column(JSON, default={}) And running the following code: p0 = Test() p1 = Test() session.add(p0) session.add(p1) session.commit() p0.json # {} p1.json # {} p0.json['US'] = 999 p1.json = {'US': 999} p0.json == p1.json # True session.commit() p0.json # {} p1.json # {'US': 999} p0.json == p1.json # False I'm running the latest version of SQLAlchemy (1.1.11 on Python 3.6). Any thoughts, please? Thanks, Andrew -- 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.