9cf2f9f298
This will remove imports from __future__ that are no longer needed. https://docs.python.org/3.5/library/2to3.html#2to3fixer-future
50 lines
1.2 KiB
Python
50 lines
1.2 KiB
Python
""" Utility functions related to database queries """
|
|
|
|
|
|
from django.conf import settings
|
|
|
|
|
|
_READ_REPLICA_DB_ALIAS = "read_replica"
|
|
|
|
|
|
def use_read_replica_if_available(queryset):
|
|
"""
|
|
If there is a database called 'read_replica',
|
|
use that database for the queryset / manager.
|
|
|
|
Example usage:
|
|
queryset = use_read_replica_if_available(SomeModel.objects.filter(...))
|
|
|
|
Arguments:
|
|
queryset (QuerySet)
|
|
|
|
Returns: QuerySet
|
|
"""
|
|
return (
|
|
queryset.using(_READ_REPLICA_DB_ALIAS)
|
|
if _READ_REPLICA_DB_ALIAS in settings.DATABASES
|
|
else queryset
|
|
)
|
|
|
|
|
|
def read_replica_or_default():
|
|
"""
|
|
If there is a database called "read_replica",
|
|
return "read_replica", otherwise return "default".
|
|
|
|
This function is similiar to `use_read_replica_if_available`,
|
|
but is be more syntactically convenient for method call chaining.
|
|
Also, it always falls back to "default",
|
|
no matter what the queryset was using before.
|
|
|
|
Example usage:
|
|
queryset = SomeModel.objects.filter(...).using(read_replica_or_default())
|
|
|
|
Returns: str
|
|
"""
|
|
return (
|
|
_READ_REPLICA_DB_ALIAS
|
|
if _READ_REPLICA_DB_ALIAS in settings.DATABASES
|
|
else "default"
|
|
)
|