[Django]-Django – Prevent automatic related table fetch

After some more digging, I’ve found the place in the code to do this.

The file in question is django/db/models/fields/related.py

You need to insert two lines into this file.

Locate class “SingleRelatedObjectDescriptor”. You need to change the function __get__() as follows:

def __get__(self, instance, instance_type=None):
    if instance is None:
        return self
    try:
        return getattr(instance, self.cache_name)
    except AttributeError:
        raise Exception("Automated Database Fetch on %s.%s" % (instance._meta.object_name, self.related.get_accessor_name()))
        # leave the old code here for when you revert!

Similarly, in class “ReverseSingleRelatedObjectDescriptor” further down the code, you again need to change __get__() to:

def __get__(self, instance, instance_type=None):
    if instance is None:
        return self

    cache_name = self.field.get_cache_name()
    try:
        return getattr(instance, cache_name)
    except AttributeError:
        raise Exception("Automated Database Fetch on %s.%s" % (instance._meta.object_name, self.field.name))
        # BEWARE: % parameters are different to previous class
        # leave old code here for when you revert

Once you’ve done this, you’ll find that Django raises an exception every time it performs an automatic database lookup. This is pretty annoying when you first start, but it will help you track down those pesky database lookups. Obviously, when you’ve found them all, it’s probably best to revert the database code back to normal. I would only suggest using this during a debugging/performance investigation phase and not in the live production code!