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Django query optimization supports for multi db relations.

Project description

# django-multi-db-relation

> Queryset optimization supports for multi database spanning relations between Django models.

## Requirements

- Python (>= 3.5)
- Django (>= 1.10)

## Installation

pip install django-multi-db-relation

## Usage

For models

class ModelA(models.Model):
name = models.CharField(max_length=10)

class ModelB(models.Model):
a = models.ForeignKey(ModelA, on_delete=models.DO_NOTHING)

class ModelC(models.Model):
b = models.ForeignKey(ModelB, on_delete=models.DO_NOTHING, db_constraint=False)

suppose that `ModelA` and `ModelB` is routed to `db1` and `ModelC` to `db2`.

We **cannot** run a queryset with `select_related()`.

>>> ModelC.objects.select_related('b') # Table not found

In this case, modify `ModelC` like:

from multi_db_relation.mixins import ExternalDbQuerySetMixin

class ModelCQuerySet(ExternalDbQuerySetMixin, models.QuerySet):

class ModelC(models.Model):
b = models.ForeignKey(ModelB, on_delete=models.DO_NOTHING, db_constraint=False)

objects = models.Manager.from_queryset(queryset_class=ModelCQuerySet)()

class Meta:
external_db_fields = ['b']


>>> ModelC.objects.select_related('b') # Number of queries is optimized from O(n) to O(1)
>>> ModelC.objects.select_related('b__a') # Also works well

## License


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