Filtered Query Set

[snoba]

I have a scenario that I need to retrieve records from a model, that satisfy certain conditions.
For example, the request could be described as:
"SELECT * FROM model WHERE column_1='value_1' AND column_2='value_2'
How could I implement this? Actually, I saw the examples, but I don't have an efficient idea to do this.
Would you please help me in View definition or refer to proper sample?

[snoba]

I found a solution. It seems that we should implement a get_queryset(self) method to apply targeted filters:

    def get_queryset(self):
        return Entity.objects.filter('item_1'='value_1')

While this could results in proper table values, but, the performance of loading decreases significantly.
Is there any idea on having filtering without performance issues?