Why django ORM is much slower than raw SQL

Question

I have the following two pieces of code:

First, in SQL:

self.cursor.execute('SELECT apple_id FROM main_catalog WHERE apple_id=%s', apple_id) if self.cursor.fetchone(): print '##' 

Next, in Django:

 if Catalog.objects.filter(apple_id=apple_id).exists(): print '>>>' 

Performing this first method is about 4 times faster than the second path in a loop of 100 thousand records. Which explains that Django is much slower?

Answer 1

Typically, ORMs are faced with the problem of instantiating an object for each row and returning it. Your raw SQL does not do this, so it won’t take the penalty. For large result sets where you are not going to use an object, it is better to bypass ORM.