Re: guc patch: Make variables fall back to default values

On Tue, Mar 13, 2007 at 10:19:54AM -0400, Tom Lane wrote:
> Gregory Stark <stark(at)enterprisedb(dot)com> writes:
> > It's not just a bug. There's code missing.

> > The code seems to assume that all custom variables are strings. There are
> > about half a dozen Assert(variable->vartype == PGC_STRING) throughout the
> > patch. That's not true, plperl's use_strict is a boolean and we have
> > DefineCustome*Variable functions for each type of variable.

> Well, they *are* strings as long as they're "custom". Once a
> DefineCustomFoo has been executed, there (should be) no difference
> between a "custom" variable and a hard-wired one.

The code in question is the only place that calls one of the
DefineCustom*Variable functions. But those functions set
var->group = CUSTOM_OPTIONS what makes variables look like custom variables
defined via SQL or the config file but in reality they aren't. Hence the
confusion of the type assertion.

> The thing that I was wondering about is the same Joachim mentioned: how
> is it that the regression test ever worked? The answer is that it's
> not really testing custom variables, because it doesn't try to set
> plperl.use_strict until after plperl has been loaded into the current
> session. So by that time the variable exists and should look like a
> perfectly ordinary boolean GUC variable. The fact that it doesn't look
> like that says to me that there's something wrong with the patch logic,
> over and above the question of what it should be Asserting.

What is wrong is that plperl defines a variable that is a mix of a guc
variable and a custom variable. It claims being a custom variable by setting
var->group = CUSTOM_OPTIONS but it does not set the respective
custom_variable_class and so by definition it can't be a custom variable.

Joachim