Re: [9.2] Confusion over CacheRegisterSyscacheCallback

On Tue, Mar 06, 2012 at 11:10:38AM -0500, Tom Lane wrote:
> Marko Kreen <markokr(at)gmail(dot)com> writes:
> > So my question is that after doing generic SearchSysCache() like:
>
> > tup = SearchSysCache(USERMAPPINGUSERSERVER,
> > ObjectIdGetDatum(user_mapping->userid),
> > ObjectIdGetDatum(foreign_server->serverid),
> > 0, 0);
>
> > what is the proper way to calculate the hashValue that
> > will be given to callback?
>
> Why would you need to know that? The reason the calculation function
> is static is that there's no apparent need to expose that information
> outside the syscache subsystem.

Because I need to invalidate my own internal state that corresponds
to particular system catalog row?

In current case (plproxy) I need to invalidate libpq connections
that are created from particular foreign server entry.

--
marko