Re: Fwd: Procedural Languages

Michael Nolan wrote:
> On Thu, May 31, 2012 at 2:23 PM, Darren Duncan <darren@darrenduncan.net> wrote:
>     Michael Nolan wrote:
>
>         PL/pgSQL and PL/perlu are the only ones I use.  I use PL/perlu
>         primarily to launch shell scripts from triggers, for example to
>         update an external website when a row in a table has been
>         inserted, deleted or updated.
>
>     There is also another way to do what you describe that might be more
>     secure.
>
>     Rather than having the DBMS launch shell scripts directly, instead
>     use LISTEN/NOTIFY messaging, where the trigger posts a message, and
>     you have an ordinary client script listening for them, and the
>     client script launches the shell scripts when it gets a message.
>
>     This way, you need a persistent client script, but you don't need to
>     invoke the shell in the DBMS ... or use the untrusted version of
>     PL/Perl if that's all it was for.
>
> Anybody have examples of a persistent client script?

Not a whole one.  But you can make a simple daemon in Perl, either by hand or
using some CPAN module.

The Postgres-related part though, see
http://search.cpan.org/dist/DBD-Pg/Pg.pm#pg_notifies for how the client script
talks to Postgres for this message passing.

Hopefully that'll answer the more interesting part for you.

-- Darren Duncan