Re: [HACKERS] [PATCH] A hook for session start

On Fri, Jul 21, 2017 at 9:35 AM, Yugo Nagata <nagata@sraoss.co.jp> wrote:
>
> On Fri, 21 Jul 2017 09:53:19 +0800
> Craig Ringer <craig@2ndquadrant.com> wrote:
>
> > On 21 July 2017 at 08:42, Robert Haas <robertmhaas@gmail.com> wrote:
> >
> > > On Thu, Jul 20, 2017 at 8:27 AM, Fabrízio de Royes Mello
> > > <fabriziomello@gmail.com> wrote:
> > > > I'm not sure your real needs but doesn't it material for improve Event
> > > > Triggers???
> > >
> > > I've thought about that, too.  One problem is what to do if the user
> > > hits ^C while the event trigger procedure is running.  If you respond
> > > to that by killing the event trigger and letting the user issue
> > > commands, then the event trigger can't be used for security or
> > > auditing purposes because the user might prevent it from doing
> > > whatever it's intended to do with a well-timed interrupt.  If you
> > > ignore ^C or make it turn into FATAL, then a poorly-crafted trigger
> > > can lock users out of the database.  Maybe that's OK.  We could say
> > > "well, if you lock yourself out of the database with your logon
> > > trigger, you get to shut down the database and restart in single user
> > > mode to recover".
> > >
> > > A hook, as proposed here, is a lot simpler and lacks these concerns.
> > > Installing code in C into the database is intrinsically risky
> > > anywhere, and not any moreso here than elsewhere.  But it's also less
> > > accessible to the average user.
> > > <http://www.postgresql.org/mailpref/pgsql-hackers>
> >
> >
> > I'd favour the c hook personally. It's a lot more flexible, and can be used
> > by an extension to implement trigger-like behaviour if anyone wants it,
> > including the extension's choice of error handling decisions.
> >
> > It's also a lot simpler and less intrusive for core. Which is nice where we
> > don't have something that we don't have anything compelling destined for
> > core that needs it. (I want to add a bunch of hooks in the logical
> > replication code in pg11 for similar reasons, and so features like DDL
> > replication can be prototyped as extensions more practically).
> >