Re: Prevent conflicting SET options from being set

"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes
>
> We already have the ability to issue custom messages in assign_hooks,
> and I think that's sufficient in practice.

Yes, I agree this is already sufficient - seems we need to remove that TODO
item in the list.

>
> A bigger problem with making cross-variable validity checks is that you
> can't really do it per-variable without falling foul of ordering
> considerations. For instance, the existing checks in
> assign_stage_log_stats and assign_log_stats are ill-considered because
> they may reject a postgresql.conf file that turns one variable on before
> turning the other off.
>

This problem also applies to "debug_pretty_print" and "debug_print_parse". A
possible but costly solution is that after each SET, we have to validate
*all* the GUC variables again to see if there is any conflicts.

Regards,
Qingqing