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
class A(db.Model):
__tablename__ = 'a'
id = db.Column(db.Integer, primary_key=True)
column1 = db.Column('column1', JSON, nullable=False, default=JSON.NULL)
_column2 = db.Column('column2', JSON, nullable=False, default=JSON.NULL)
a = A(column1=None, column2=None)
db.session.add(a)
# Expected
print a.column1 # None
print a._column2 # None
# Unexpected differences
db.session.flush()
print a.column1 # None
print a.column2 # symbol('JSON_NULL')
db.session.commit()
print a.column1 # None
print a.column2 # None
I believe this is expected given the bug listed above. However, I have a
question about how to handle this even when the original bug is fixed.
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.
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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