From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
---|---|
To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
Cc: | Dimitri Fontaine <dimitri(at)2ndQuadrant(dot)fr>, Markus Wanner <markus(at)bluegap(dot)ch>, kaigai(at)kaigai(dot)gr(dot)jp, PostgreSQL-development Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Review: Extra Daemons / bgworker |
Date: | 2012-11-30 12:59:15 |
Message-ID: | 20121130125915.GE3957@awork2.anarazel.de |
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Lists: | pgsql-hackers |
On 2012-11-30 09:57:20 -0300, Alvaro Herrera wrote:
> Dimitri Fontaine wrote:
> > Markus Wanner <markus(at)bluegap(dot)ch> writes:
> > > AFAICS pgqd currently uses libpq, so I think it would rather turn into
> > > what I call a background worker, with a connection to Postgres shared
> > > memory. I perfectly well see use cases (plural!) for those.
> > >
> > > What I'm questioning is the use for what I rather call "extra daemons",
> > > that is, additional processes started by the postmaster without a
> > > connection to Postgres shared memory (and thus without a database
> > > connection).
> >
> > I totally missed the need to connect to shared memory to be able to
> > connect to a database and query it. Can't we just link the bgworkder
> > code to the client libpq library, just as plproxy is doing I believe?
>
> One of the uses for bgworkers that don't have shmem connection is to
> have them use libpq connections instead. I don't really see the point
> of forcing everyone to use backend connections when libpq connections
> are enough. In particular, they are easier to port from existing code;
> and they make it easier to share code with systems that still have to
> support older PG versions.
They also can get away with a lot more crazy stuff without corrupting
the database. You better know something about what youre doing before
doing something with direct shared memory access.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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