Re: [HACKERS] Undefined psql variables

Corey Huinker <corey.huinker@gmail.com> writes:
> I was giving some thought to how psql handles undefined variables.
> I would like an option where either psql can provide an alternate value
> when an undefined variable is referenced, or a way to detect that a
> specific variable is undefined and replace it with a defined variable.

This seems pretty bizarre.  What's the use case?  Why would it not
be better to build the behavior out of other spare parts, along the
lines of COALESCE or perhaps
     \if not defined(x)     \set x y     \fi

Obviously the \if stuff is things we don't have yet either, but
it seems less likely to have surprising side-effects.
        regards, tom lane