Re: PREPARE/EXECUTE across backends?

On Wed, Oct 01, 2003 at 09:01:23PM -0400, Neil Conway wrote:
> On Wed, 2003-10-01 at 20:25, Jingren Zhou wrote:
> > From the document, it seems that PREPARE/EXECUTE works only in the same
> > session. I am wondering whether postgres can prepare a query (save the plan)
> > for difference backends.
>
> The decision to store prepared statements per-backend, rather than in
> shared memory, was made deliberately. In fact, an early version of the
> PREPARE/EXECUTE patch (written by Karel Zak) stored prepared statements
> in shared memory. But I decided to remove this, because:

> That's all the reasons I can think of off the top of my head for doing
> things the way we do. However, I'm open to being convinced: if you think
> we should store prepared statements in shm, feel free to make a case for
> it.

I think the current non-shared PREPARE/EXECUTE is right solution. The
shared version require define new type of memory managment routines
which is full compatible with the standard and abstract PostgreSQL mmgr
tier. I worked on this because it was interesting experiment and now
we know that write something like this is possible :-)

I think final and right solution are persisten pre-forked backends
which know to keep cached PREPARE/EXECUTE stuff (and a lot of others
things) in own memory. It's nice and simple solution than use shared
memory.

Karel

--
Karel Zak <zakkr(at)zf(dot)jcu(dot)cz>
http://home.zf.jcu.cz/~zakkr/