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
> <javascript:>> 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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