Re: Advice regarding configuration parameters

Tom Lane wrote:
> What do you think of the idea of suppressing the "unknown variable" 
> error for some class of variable names?

I like it. I wonder if we ought to have a way to "register" valid
classes? Maybe a new guc variable in the form of a list of valid
classes. So something like:

custom_variable_class = 'plr,pljava'
plr::foo = '/usr/lib/R'
pljava::baz = 1
plruby::var = true        <== this one would generate an error

> If we had agreement on doing that then I think the rest would be
> pretty simple.  After a few moments' thought I like the following
> sketch:

[good implementation ideas]

> This scheme could not handle add-on GUC variables with some of the
> odder flags, such as GUC_LIST_INPUT, since the correct flag values
> wouldn't be known when the input is first seen.

I think this is OK.

> And we'd have to think a little about how to handle variable values
> that are discovered to be erroneous when we try to assign them to the
> variable --- probably we can just drop them, but does that make the
> semantics weird at all?

Maybe we can require a default value as a parameter to 
add_guc_variable() and use that?

Joe