there's no "eager" strategy. you'd want something like lazy="joined" or
something like that. check the docs.
On 06/01/2016 04:19 PM, Horcle wrote:
Hi Mike,
Just verifying:
Should
class Patient(Model):
encounters = relationship(
"Encounter",
backref_populates='patient',
lazy='dynamic')
be
class Patient(Model):
encounters = relationship(
"Encounter",
back_populates='patient',
lazy='dynamic')
If this is true, I am getting an error that
Exception: can't locate strategy for <class
'sqlalchemy.orm.relationships.RelationshipProperty'> (('lazy', 'eager'),)
Btw, we rebuilt the database using patient_id as a primary key.
Thanks for your help!
Greg--
On Tuesday, May 31, 2016 at 3:49:29 PM UTC-5, Mike Bayer wrote:
you should use "dynamic" and your relationships are mis-configured with
mis-use of the backref() construct, as you've constructed relationships
on both sides that are mutual you'd use back_populates:
class Encounter(Model):
patient = relationship(
"Patient",
back_populates='encounters',
lazy='eager')
class Patent(Model):
encounters = relationship(
"Encounter",
backref_populates='patient',
lazy='dynamic')
Also the foreign key from Encounter.patient_id to Patient.patient_id
does not illustrate a unique index in use and will not be accepted by
all database backends as a real constraint unless one is added (and
regardless, performance will suffer without an index on this column).
Typically, Encounter.patient_id would refer to the primary key of
Patient which is Patient.id.
On 05/31/2016 04:38 PM, Horcle wrote:
> I guess my question is: How can I efficiently load Patient and its
> related Encounters? I have tried various loading strategies of
dynamic,
> joined (I would think this would be the desired option), subquery, no
> load, etc., and it these do not load. On the other hand, I can load
> Encounter just fine and access an instance of the Patient object.
>
>
>
> On Tuesday, May 31, 2016 at 11:20:37 AM UTC-5, Horcle wrote:
>
> I have the following two models:
>
> |
> ClassEncounter(Model):
> __tablename__ ='cp_service'
> id =Column(Integer,primary_key=True,autoincrement=True)
> master_service_id =Column(String(255))
> admission_datetime =Column(DateTime)
> admission_provider_id =Column(String(255))
> admission_status =Column(String(255))
> age_at_visit =Column(String(255))
> attending_provider_id =Column(String(255))
> center =Column(String(255))
> department_name =Column(String(255))
> discharge_datetime =Column(DateTime)
> encounter_category =Column(String(255))
> encounter_class =Column(String(255))
> encounter_date =Column(DateTime)
> encounter_setting =Column(String(255))
> encounter_type =Column(String(255))
> primary_care_provider_id =Column(String(255))
> primary_service_yn =Column(String(255))
> provider_id =Column(String(255))
> serv_area_id_orig =Column(String(255))
> service_id =Column(Integer)
> patient_id
=Column(Integer,ForeignKey('cp_patient.patient_id'))
> patient
>
=relationship("Patient",backref=backref("patientEncounter"),lazy='eager',primaryjoin="Patient.patient_id==Encounter.patient_id")
> |
>
> |
> classPatient(Model):
> __tablename__ ='cp_patient'
> id =Column(Integer,primary_key=True,autoincrement=True)
> first_name =Column(String(100))
> middle_name =Column(String(80))
> last_name =Column(String(80))
> sex =Column(String(80))
> race =Column(String(80))
> birth_date =Column(DateTime)
> ethnicity =Column(String(80))
> race =Column(String(80))
> patient_id =Column(Integer)
> mrn =Column(String(80))
> title =Column(String(80))
> suffix =Column(String(80))
> name_alias =Column(String(80))
> addr_1 =Column(String(80))
> addr_2 =Column(String(80))
> addr_3 =Column(String(80))
> city =Column(String(80))
> state =Column(String(80))
> country =Column(String(80))
> zip =Column(String(80))
> encounter
>
=relationship("Encounter",backref=backref("Patient"),lazy='dynamic',primaryjoin="Patient.patient_id==Encounter.patient_id")
> |
>
>
> Where one patient can have many encounters.
>
> I am able to load the patent model fine in a scaffolded list
when I
> comment out the encounter relationship in the last line (there
are
> roughly 35K patients), but when I link it to Encounters (1.7
> million), then I am running into major performance issues. I
tried
> using lazy='dynamic', but got an error that:
> |
> Onrelationship Encounter.patient,'dynamic'loaders cannot be used
> withmany-to-one/one-to-one relationships and/oruselist=False.
> |
>
> What other options are there available to not load all the
relations
> until needed?
>
> Thanks!
>
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