Include values of different table in django models - django

Question

I'm trying to check if files reported in one system exist in a different system. The models belong to different tables in different databases. They have no relationship other than the name in common.
I'm using django rest framework to serialize the values of one table and I'd like to include the values of the other table in one efficient way. The way I'm currently doing, makes too many queries! My question is: Is there a way to improve this performance issue?
Here is an example of what I have
# model1
class Product(models.Model):
name = models.CharField(max_length=50)
# model2 (different database)
class Files(models.Model):
name = models.CharField(max_length=50)
filename = models.CharField(max_length=50)
And my view set is
class ProductViewSet(viewsets.ModelViewSet):
queryset = Inventory.objects.all()
serializer_class = ProductSerializer
I managed to get the result as I said (not efficiently, though) in two different ways:
1) Including the fields in the serializer
class ProductSerializer(serializers.ModelSerializer):
has_png = serializers.SerializerMethodField('has_png')
has_jpg = serializers.SerializerMethodField('has_jpg')
def has_png(self, product):
# I wish I could avoid this code duplication too...
# I'm basically using the same code in two functions
files = Files.objects.filter(name=product.name)
filtered_files = files.filter(filename__startswith='png')
return filtered_files.exists()
def has_bam(self, product):
files = Files.objects.filter(name=product.name)
filtered_files = files.filter(filename__istartswith='jpg')
return filtered_files.exists()
Meta:
model = Product
2) Including properties in my model1 which is serialized
class Product(modes.Model):
name = models.CharField(max_length=50)
def _get_png(self):
# I tried to cache this query in a different function but didn't work
files = Files.objects.filter(name=self.name)
filtered_files = files.filter(filename__istartswith='png')
return filtered_files.exists()
def _get_jpg(self):
files = Files.objects.filter(name=self.name)
filtered_files = files.filter(filename__istartswith='jpg')
return filtered_files.exists()
has_png = property(_get_png)
has_jpg = property(_get_jpg)
and then I add in the serializer:
class ProductSerializer(serializers.ModelSerializer):
has_fastq = serializers.ReadOnlyField()
has_bam = serializers.ReadOnlyField()
Meta:
model = Product

Answer 1

you can try to use cached_property
from django.db.models.functions import Lower
from django.utils.functional import cached_property
class Product(modes.Model):
name = models.CharField(max_length=50)
#cached_property
def file_formats(self):
files = Files.objects.filter(name=self.name)
files = files.annotate(lower_format=Lower('file_format')))
return files.values_list('lower_format', flat=True)
def _get_png(self):
return 'png' in self.file_formats
def _get_jpg(self):
return 'jpg' in self.file_formats
has_png = property(_get_png)
has_jpg = property(_get_jpg)