Hi,
I'm using the UniqueObject recipe [1] for simple two column tables
and it works just fine, but what is the best way to use it with tables
containing relationships?
I usually did:
mytime = Timestamp.as_unique(session, timestamp=value)
session.flush()
fingerprint = Fingerprint.as_unique(session, fingerprint='foo',
ts_id=mytime.id)
Fingerprint class looks like this (timestamp is optional):
class Fingerprint(UniqueMixin, Base):
__tablename__ = 'fingerprint'
id = Column(mysql.MEDIUMINT(unsigned=True), primary_key=True)
fingerprint = Column(mysql.CHAR(16), nullable=False)
ts_id = Column(mysql.SMALLINT(unsigned=True),
ForeignKey('timestamp.id'))
timestamp = relationship('Timestamp')
@classmethod
def unique_hash(cls, **kw):
return str(kw)
@classmethod
def unique_filter(cls, query, fingerprint, ts_id=None):
return query.filter(Fingerprint.fingerprint == fingerprint,
Fingerprint.ts_id == ts_id)
to get rid of session.flush() I changed it to (which gave me a >100%
speedup):
mytime = Timestamp.as_unique(session, timestamp=value)
fingerprint = Fingerprint.as_unique(session, fingerprint='foo',
timestamp=mytime)
(also adjusting the unique_filter() to: ...,
Fingerprint.timestamp==timestamp)
but it also shows this warning:
/usr/lib64/python2.7/site-packages/sqlalchemy/orm/relationships.py:1392:
SAWarning: Got None for value of column timestamp.id; this is
unsupported for a relationship comparison and will not currently produce
an IS comparison (but may in a future release)
"(but may in a future release)" % column)
Is it ok to use the latter way? (will it result in the same table
content?)
thanks,
Marten
[1]
https://bitbucket.org/zzzeek/sqlalchemy/wiki/UsageRecipes/UniqueObject
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