Re: Extensions and custom_variable_classes

On Mon, Dec 20, 2010 at 3:56 AM, Dimitri Fontaine
<dimitri@2ndquadrant.fr> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> I bet it doesn't.  The *postmaster* never connects to a database, so
>> which copy of pg_extension does it ever read?
>
> None, which does it need to read? My answer is none, you're saying it's
> wrong, I don't get why. postmaster surely has no business with what's in
> a specific database and no use at all of placeholder GUCs, right?

Let's take a concrete example.  Suppose the user installs the
extension 'pg_stat_statements' and puts the following into their
postgresql.conf:

pg_stat_statements.max = 31415;

The effect of that has to be that the postmaster adds a certain amount
of space to PostgreSQL's initial shared memory allocation.  That means
the postmaster has to know that pg_stat_statements is a valid custom
variable class.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company