On Nov 23, 2014, at 1:07 PM, Rick van Hattem <wo...@wol.ph> wrote:
> > Not really, cause psycopg already fetched everything.
>
> Not if Django limits it by default :)
Unfortunately, that's not how it works. There are three things that take up
memory as the result of a query result:
1. The Django objects. These are created in units of 100 at a time.
2. The psycopg2 Python objects from the result. These are already limited to a
certain number (I believe to 100) at a time.
3. The results from libpq. These are not limited, and there is no way of
limiting them without creating a named cursor, which is a significant change to
how Django interacts with the database.
In short, without substantial, application-breaking changes, you can't limit
the amount of memory a query returns unless you add a LIMIT clause to it.
However, adding a LIMIT clause can often cause performance issues all by itself:
http://thebuild.com/blog/2014/11/18/when-limit-attacks/
There's no clean fix that wouldn't have significant effects on unsuspecting
applications.
--
-- Christophe Pettus
x...@thebuild.com
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