Django all related data - django

Question

class Docs(models.Model):
doc_id = models.BigIntegerField(primary_key=True)
journal = models.CharField(max_length=50, blank=True, null=True)
year = models.IntegerField(blank=True, null=True)
class Meta:
managed = False
db_table = 'docs'
class Assays(models.Model):
assay_id = models.BigIntegerField(primary_key=True)
doc = models.ForeignKey('Docs', models.DO_NOTHING)
description = models.CharField(max_length=4000, blank=True, null=True)
class Meta:
managed = False
db_table = 'assays'
class Activities(models.Model):
activity_id = models.BigIntegerField(primary_key=True)
assay = models.ForeignKey(Assays, models.DO_NOTHING)
doc = models.ForeignKey(Docs, models.DO_NOTHING, blank=True, null=True)
record = models.ForeignKey('CompoundRecords', models.DO_NOTHING)
class Meta:
managed = False
db_table = 'activities'
I apologize in advance if this answer is easily found elsewhere. I have searched all over and do not see a simple way to query my data as intuitively as I feel like should be possibe.
These are classes for 3 tables. The actual dataset is closer to 100 tables. Each doc_id can have one or many associated activity_ids. Each activity_id is associated with one assay_id.
My goal is to obtain all of the related data for each of the activities in a single doc. For instance:
query_activities_values = Docs.objects.get(doc_id=5535).activities_set.values()
for y in query_activities_values:
print(y)
break
>>> {'activity_id': 753688, 'assay_id': 158542, 'doc_id': 5535, .....
This returns 32 dictionaries (only part of the first is shown) for columns in the Activities table that have doc_id=5535. I would like to go one step further and also automatically pull in all of the data from the Assays table that is associated with the corresponding assay_id for each dictionary.
I can access that Assay data through a similar query, but only by stating each field explicitly:
query_activities_values = Docs.objects.get(doc_id=5535).activities_set.values('assay', 'assay__assay_type', 'assay__description')
for y in query_activities_values:
print(y)
break
I would like a single query that finds not only the assay and associated assay data for one activity_id, but finds all data and associated data for the 90+ other tables associated in the model
Thank you
Update 1
I did find this code that works surprisingly well for my needs, however, I was curious if this is the best method:
from django.forms.models import model_to_dict
def serial_model(modelobj):
opts = modelobj._meta.fields
modeldict = model_to_dict(modelobj)
for m in opts:
if m.is_relation:
foreignkey = getattr(modelobj, m.name)
if foreignkey:
try:
modeldict[m.name] = serial_model(foreignkey)
except:
pass
return modeldict
That's not too much code, but I thought there may be a more built-in way to do this.

Answer 1

What you need is prefetch_related:
Django 2.2 Prefetch Related Docs
query_activities_values = Docs.objects.get(doc_id=5535).activities_set.values()
Would become:
query_activities_values = Docs.objects.prefetch_related(models.Prefetch("activities_set", to_attr="activities"), models.Prefetch("assays_set", to_attr="assays")).get(doc_id=5535)
A new attributes will be created called "activities" and "assays" which you can use to retrieve data.
One more thing. This isn't actually 1 query. It's 3. However, if you're getting more than just one object from Docs, it's still going to be 3.
Also, is there a reason why you're using BigIntegerField?