It looks like I needed to define the columns inside my class. That's the
only difference between your class and mine. And I tested out the query
and it now works, and returns the correct number of rows.
In [4]: print
session.query(datadb.Sample.pk).filter(datadb.Sample.nsa_logmstar < 9)
SELECT datadb.sample.pk AS datadb_sample_pk
FROM datadb.sample
WHERE log(datadb.sample.nsa_mstar) < %(log_1)s
In [6]:
len(session.query(datadb.Sample.pk).filter(datadb.Sample.nsa_logmstar <
9,datadb.Sample.nsa_mstar > 0).all())
Out[6]: 273
Do you have any idea why the column definition matters here? Thanks for
all your help.
Brian
On Friday, January 15, 2016 at 5:02:03 PM UTC-5, Brian Cherinka wrote:
>
> Here is the print immediately after my original class definition:
>
> print 'sample nsa log mstar', Sample.nsa_logmstar
>
> and the result
>
> sample nsa log mstar None
>
> When I run your script exactly as is, I get the same output as you.
>
> When I replace my class definition with yours, inside my code, as follows
>
> class Sample(Base):
> __tablename__ = 'sample'
> __table_args__ = {'autoload' : True, 'schema' : 'mangadatadb'} (I
> needed to add this line in)
>
> pk = Column(Integer, primary_key=True)
> nsa_mstar = Column(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 func.log(cls.nsa_mstar)
>
> now the print statement : print 'sample nsa log mstar',
> Sample.nsa_logmstar
> returns
>
> sample nsa log mstar log(mangadatadb.sample.nsa_mstar)
>
>
> On Friday, January 15, 2016 at 4:28:31 PM UTC-5, Simon King wrote:
>>
>> 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 <havo...@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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