Re: Poor plan when using EXISTS in the expression list

On Thursday, October 4, 2018 4:46:26 PM CEST Geoff Winkless wrote:
> On Thu, 4 Oct 2018 at 13:11, Pierre Ducroquet <p(dot)psql(at)pinaraf(dot)info> wrote:
> > Our developpers ORM (Django's) sadly can not use EXISTS in the where
> > clauses
> > without having it in the expression part of the SELECT statement.
>
> I don't know if this will be helpful to you (and I appreciate there's still
> the underlying PG issue), but there's a suggestion here that you can work
> around this using .extra()
>
> https://stackoverflow.com/a/38880144/321161

Sure this helps when you know the trap and don't use the Exist support in
Django, but this still mean any developer with Django may create a query that,
on small volumes, will be a bit slow, and will blow up on big volumes. We
sadly can not monitor every piece of code written by developers or imported in
the dependencies.