Fixed #33025 -- Avoided accessing the database connections in Query.build_lookup() when not necessary.
Fixed #33025 -- Avoided accessing the database connections in Query.build_lookup() when not necessary.

Of the built-in backends, only Oracle treats empty strings and nulls as
equal, so avoid testing the default connection backend for
interprets_empty_strings_as_nulls if it can be established from the
lookup that it wouldn't affect the lookup instance returned. This
improves performance a small amount for most lookups being built,
because accessing the connections requires touching the thread critical
`Local` which is an expensive operation.

blighj/django,pauloxnet/django,MarkusH/django,ghickman/django,monetate/django,solarissmoke/django,rsalmaso/django,ghickman/django,atul-bhouraskar/django,shaib/django,takis/django,django/django,pauloxnet/django,solarissmoke/django,shaib/django,shaib/django,manhhomienbienthuy/django,MarkusH/django,manhhomienbienthuy/django,felixxm/django,apollo13/django,ghickman/django,pauloxnet/django,shaib/django,blighj/django,felixxm/django,rsalmaso/django,auvipy/django,dsanders11/django,pauloxnet/django,felixxm/django,takis/django,takis/django,dsanders11/django,monetate/django,django/django,auvipy/django,django/django,atul-bhouraskar/django,rsalmaso/django,solarissmoke/django,MarkusH/django,rsalmaso/django,manhhomienbienthuy/django,takis/django,atul-bhouraskar/django,monetate/django,ghickman/django,felixxm/django,atul-bhouraskar/django,auvipy/django,solarissmoke/django,dsanders11/django,apollo13/django,django/django,apollo13/django,blighj/django,MarkusH/django,apollo13/django,dsanders11/django,auvipy/django,blighj/django,monetate/django,manhhomienbienthuy/django