Re: Add read-only param to set_config(...) / SET that effects (atleast) customized runtime options

On 04/20/2018 04:18 PM, Chapman Flack wrote:
> On 04/20/2018 04:03 PM, Andrew Gierth wrote:

>> Assign hooks aren't allowed to throw errors under any circumstance
>> because they're called during transaction abort, and throwing an error
>> during abort is obviously not tolerable.
> 
> Ah yes, now you remind me, that was why I had put my extension idea
> on the table at the time.
> 
> It seems as if, for any of these ideas (cookie-protection of GUCs
> or just SET READONLY for GUCs), at least some small patch to core
> will be prerequisite, to allow either a flag or a reset check hook
> able to make RESET skip protected GUCs.

I suppose an extension could protect a GUC of its own from reset
without the cookie, despite the lack of a reset hook in core, by
simply maintaining its own copy of the original reset value, and
stuffing the protected value into the variable's reset_val for
the duration, no?

Wouldn't be usable to protect core GUCs, but could provide an API
for other extensions to make their GUCs protectable, by passing the
config_* struct pointer to a registration function.

-Chap