On Tue, Jul 18, 2017 at 2:12 AM, <vin...@benchling.com> wrote:
> A related issue (that seems like a bug) happens when reading attribute
> values after a flush, but before a commit. In this scenario, I set the
> default=JSON.NULL in both columns
> With "default=JSON.NULL", it seems like the value of a.column1 can be None
> OR symbol('JSON_NULL') depending on if it is read 1) before flush, 2) after
> flush, and 3) after commit. Are there any suggested ways of dealing with
> this? (Or it's possible I'm doing something wrong here!) We have code that
> checks "if a.column1 is None", which is failing with the 1.1.11 upgrade.
this actually depends on if you explicitly set the value in Python.
In your example, you're setting the value to None so that None is what
you'll see in Python. It's only if you omit the "None" from Python
that we need the "default" to do the translation. JSON.NULL is this
totally special value that the Core default mechanism doesn't yet
fully accommodate so that's why setting default=text("'null'") for now
is a workaround.
>
>
> On Monday, July 17, 2017 at 9:47:10 PM UTC-7, vin...@benchling.com wrote:
>>
>> Hello, I'd like to report a bug report regarding JSON nulls and
>> underscore-prefixed attributes as we're upgrading from 1.0.17 to 1.1.11.
>>
>> I read through the behavior at
>> http://docs.sqlalchemy.org/en/latest/changelog/migration_11.html#change-3514
>> and
>> http://docs.sqlalchemy.org/en/latest/changelog/migration_11.html#behavior-change-3514,
>> all of which makes sense to me.
>>
>> However, this does not seem to work for attributes which are prefixed with
>> an underscore. Example:
>>
>> class A(db.Model):
>> __tablename__ = 'a'
>>
>>
>> id = db.Column(db.Integer, primary_key=True)
>> column1 = db.Column('column1', JSON, nullable=False)
>> _column2 = db.Column('column2', JSON, nullable=False)
>>
>> # Succeeds
>> db.session.add(A(column1=[], _column2=[]))
>> db.session.flush()
>>
>> # Succeeds
>> db.session.add(A(column1=None, _column2=[]))
>> db.session.flush()
>>
>> # Fails with integrity error
>> db.session.add(A(column1=[], _column2=None))
>> db.session.flush()
>>
>>
>> (psycopg2.IntegrityError) null value in column "column2" violates not-null
>> constraint
>> DETAIL: Failing row contains (5, [], null).
>> [SQL: '-- manage.py:1242 in <module>\nINSERT INTO a (column1) VALUES
>> (%(column1)s) RETURNING a.id'] [parameters: {'column1': '[]'}]
>>
>> Using db.Column('column2', JSON, nullable=False, default=JSON.NULL) ends
>> up sending a JSON NULL, so basically it looks like it is ignoring explicitly
>> set None values for attributes that start with an underscore.
>>
>> This is not workflow blocking for us (I will just change our usages to
>> also use default=JSON.NULL), but wanted to file a bug report in case it's
>> something others run into as well!
>
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