[Answer]-Onetoone or foreignkey for relationship object-properties

If you have only one Bar object per Foo then use OneToOne relation. If it can be more than one Bar for single Foo then use ForeignKey.

As for “reverse” statement:

# access to Bar property of Foo in OneToOne relation
foo.bar

# access to first Bar property of Foo in ForeignKeyRelation
foo.bar_set.all().first()

In both cases it will be one SQL query, but OneToOne version looks better 🙂