Does my test script produce the right output for you in your installation?
What does the print statement immediately after the class definition produce?
Simon
> On 15 Jan 2016, at 19:10, Brian Cherinka <havok2...@gmail.com> wrote:
>
> Actually, the class definition is entirely what I posted in the original
> message. I didn't cut anything out of that. I don't define the columns in
> mine, as you did. The property nsa_logmstar is not defined anywhere else in
> the class or in any other place in this code, or in any code that interacts
> with this code.
>
> class Sample(Base,ArrayOps):
> __tablename__ = 'sample'
> __table_args__ = {'autoload' : True, 'schema' : 'datadb'}
>
> def __repr__(self):
> return '<Sample (pk={0},cube={1})'.format(self.pk,self.cube)
>
> @hybrid_property
> def nsa_logmstar(self):
> try: return math.log10(self.nsa_mstar)
> except ValueError as e:
> return -9999.0
> except TypeError as e:
> return None
>
> @nsa_logmstar.expression
> def nsa_logmstar(cls):
> return func.log(cls.nsa_mstar)
>
> My database connection is a singleton and my base is defined inside that,
> essentially
>
> engine = create_engine(database_connection_string)
> Base = declarative_base(bind=engine)
>
> Brian
>
> On Friday, January 15, 2016 at 9:43:39 AM UTC-5, Simon King wrote:
> What happens if you put the print statement immediately after the class
> definition? Is there any chance that you've got "nsa_logmstar = None"
> somewhere in your class definition?
>
> Here's a test script which appears to work:
>
> import math
>
> import sqlalchemy as sa
> import sqlalchemy.orm as saorm
> from sqlalchemy.ext.hybrid import hybrid_property
> from sqlalchemy.ext.declarative import declarative_base
>
> Base = declarative_base()
>
> class Sample(Base):
> __tablename__ = 'sample'
>
> pk = sa.Column(sa.Integer, primary_key=True)
> nsa_mstar = sa.Column(sa.Float)
>
> @hybrid_property
> def nsa_logmstar(self):
> try:
> return math.log10(self.nsa_mstar)
> except ValueError:
> return -9999.0
> except TypeError:
> return None
>
> @nsa_logmstar.expression
> def nsa_logmstar(cls):
> return sa.func.log(cls.nsa_mstar)
>
>
> if __name__ == '__main__':
> sm = saorm.sessionmaker()
> session = sm()
> print session.query(Sample.pk).filter(Sample.nsa_logmstar < 9)
>
>
> And here's the output:
>
>
> SELECT sample.pk AS sample_pk
> FROM sample
> WHERE log(sample.nsa_mstar) < :log_1
>
>
> Simon
>
>
> On Fri, Jan 15, 2016 at 2:23 PM, Brian Cherinka <havo...@gmail.com> wrote:
> Ahh. Thanks. Here is the class side then. Still None.
>
> In [14]: print datadb.Sample.nsa_logmstar
> None
>
> Brian
>
> On Friday, January 15, 2016 at 8:48:30 AM UTC-5, Simon King wrote:
> "Sample()" is an instance. "Sample" is the class. Try:
>
> print datadb.Sample.nsa_logmstar
>
> Simon
>
> On Fri, Jan 15, 2016 at 1:46 PM, Brian Cherinka <havo...@gmail.com> wrote:
> Hi Simon,
>
> Printing on the class side, I get
>
> In [11]: print datadb.Sample().nsa_logmstar
> None
>
> It looks like it's getting set to None (or remaining None). I'm not quite
> sure what this tells me, except that it's not working. Printing on in the
> instance side, I get
>
> In [12]: print cube.sample[0].nsa_mstar
> 1386160000.0
>
> In [13]: print cube.sample[0].nsa_logmstar
> 9.14181336239
>
> nsa_mstar is a column in my database table, and nsa_logmstar I want to be
> simply the log-base10 of that quantity.
>
> If this doesn't give any insight, then it will take me some time to provide a
> small script. This code is embedded into a bunch of stuff. But I'll work on
> it.
>
> Brian
>
>
> On Friday, January 15, 2016 at 5:00:51 AM UTC-5, Simon King wrote:
> On Fri, Jan 15, 2016 at 6:16 AM, Brian Cherinka <havo...@gmail.com> wrote:
> I'm trying to set up a hybrid property / expression in a custom class, that I
> can use in queries. I think I have the syntax correct, however the query
> returns the entire table, instead of the correct subset of results. And the
> where clause just indicates True rather than the correct expression.
>
>
>
> Here is my hybrid property/expression definition
>
>
> class Sample(Base,ArrayOps):
> __tablename__ = 'sample'
> __table_args__ = {'autoload' : True, 'schema' : 'datadb'}
>
> def __repr__(self):
> return '<Sample (pk={0},cube={1})'.format(self.pk,self.cube)
>
> @hybrid_property
> def nsa_logmstar(self):
> try: return math.log10(self.nsa_mstar)
> except ValueError as e:
> return -9999.0
> except TypeError as e:
> return None
>
> @nsa_logmstar.expression
> def nsa_logmstar(cls):
> return func.log(cls.nsa_mstar)
>
> The session query is
>
> session.query(Sample.pk).filter(Sample.nsa_logmstar < 9)
>
> But printing it does not show the appropriate condition. I get
>
> SELECT datadb.sample.pk AS datadb_sample_pk,
> FROM datadb.sample
> WHERE true
>
> and the results return the entire table of ~11000 rows instead of the
> expected 272 rows. What's going on here? Everything looks correct to me, but
> I can't figure it out.
>
> I'm expecting the SQL statement to look like this
>
> select s.pk
> from datadb.sample as s
> where log(s.nsa_mstar) < 9;
>
> Any thoughts? Thanks.
>
>
> I can't see anything obviously wrong with your code, but it looks like
> Sample.nsa_logmstar is not actually resolving to the hybrid property in your
> query. What happens if you "print Sample.nsa_logmstar" just before the query?
>
> Otherwise, please provide a small runnable script that demonstrates the
> problem.
>
> Simon
>
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