Hi, > - You'll almost certainly take a performance hit when connecting to the > database. If each connection to the DB is using a different user, then you > likely cannot take advantage of things like DB connection pooling. Every > request would require that a connection be built, utilized, and then torn > down. Those operations have a cost in both time and resources. > > - It likely won't scale well. Assuming you have a fair number of unique users > with concurrent connections (depending on the resources available and tuning, > this could be as little as a few dozen), your DB now has to manage at least a > single connection or Not necessarily. Django could connect to the db as a PostgreSQL superuser and middle that runs very early could use "set session authorization" to switch user.
Regards, Antonis Antonis Christofides http://djangodeployment.com On 2017-08-09 11:03, James Schneider wrote: > > > On Aug 3, 2017 1:08 AM, "guettli" <guettl...@gmail.com > <mailto:guettl...@gmail.com>> wrote: > > First I asked a similar question on the postgresql-general list. The > discussion[1] has settled there. > > Now I would love the hear what you think. > > > I am thinking about rewriting an existing application which uses > PostgreSQL via Django. > > Up to now the permission checks are done at the application level. > > Up to now queries like: "Show all items which the current user is allowed > to modify" result in complicated SQL and > this leads to slow queries. > > Up to now there is one db-user and the application does the filtering of > rows to prevent application users to see > items which they are not allowed to see. > > I guess most web applications work like this. > > I would like to reduce the "ifing and elsing" in my python code (less > conditions, less bugs, more SQL, more performance) > > One important intention for me: I would like to avoid the redundancy. As > soon as I want to query for > "Show all items which the current user is allowed to modify" I need the > permission checking in a SQL WHERE condition. > > If I implement this. Then my code which might look like this is redundant: > > {{{ > > def has_perm(obj, user): > if user.is_superuser: > return True > ... > > }}} > > > Yes, I feel farewell pain. I love Python, but I guess I will use perm > checking via SQL > WHERE for new projects in the future. What do you think? Regards, > Thomas Güttler > > [1]: > https://www.postgresql.org/message-id/e662fd8a-6001-514c-71e8-01718444f338%40thomas-guettler.de > > <https://www.postgresql.org/message-id/e662fd8a-6001-514c-71e8-01718444f338%40thomas-guettler.de> > > I thumbed through the threads on the PG list, and the best summary of the > answers you received is: > > A. Yes you can probably do that, but it would likely be extremely complicated > and Django won't necessarily make it easy. > > B. The "problem" you are trying to solve is more of a "preference" with a > questionable motive of speed increases. > > > There wasn't a great amount of support for what you are trying to do, and I > doubt you'll find much on this list. > > The DB should not be responsible for business logic (in this case, > authorization rules). DB's are only good at storing, searching, and returning > data. Data doesn't care who you are, nor does the DBMS past the table level in > most cases. > > There are several other points to consider. > > - By moving this logic in to the DB, you are almost certainly vendor locking > yourself to the DB. If your project is not distributed to others, then it may > not be an issue. If you do, abstract away the function calls as much as > possible to build an internal Python API. If you need to change the underlying > database functionality later, your application code should remain relatively > untouched, and you can send the bundle of money in labor you saved to me. ;-) > > - You'll almost certainly take a performance hit when connecting to the > database. If each connection to the DB is using a different user, then you > likely cannot take advantage of things like DB connection pooling. Every > request would require that a connection be built, utilized, and then torn > down. Those operations have a cost in both time and resources. > > - It likely won't scale well. Assuming you have a fair number of unique users > with concurrent connections (depending on the resources available and tuning, > this could be as little as a few dozen), your DB now has to manage at least a > single connection or > > > -- > You received this message because you are subscribed to the Google Groups > "Django users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to django-users+unsubscr...@googlegroups.com > <mailto:django-users+unsubscr...@googlegroups.com>. > To post to this group, send email to django-users@googlegroups.com > <mailto:django-users@googlegroups.com>. > Visit this group at https://groups.google.com/group/django-users. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-users/CA%2Be%2BciV1obpdOUpLdMQ9jwYgLOjisUcUmVbFfHOv8qKE4EQPmA%40mail.gmail.com > <https://groups.google.com/d/msgid/django-users/CA%2Be%2BciV1obpdOUpLdMQ9jwYgLOjisUcUmVbFfHOv8qKE4EQPmA%40mail.gmail.com?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Django users" group. 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