Re: COALESCE with single argument looks like identity function

Maksim Milyutin <maksim.milyutin@tantorlabs.ru> writes:
> I've noticed that COALESCE function doesn't converge to argument 
> expression if it is alone in argument list of COALESCE as part 
> simplification routine for expressions in planner. This might suppress 
> further useful transformations when non-strict ops are required from 
> some expression like converging OUTER JOIN to INNER one with WHERE qual 
> containing COALESCE over single column from inner side.

Seems like a reasonable idea --- it's probably a rare case, but the
check is cheap enough.  I'd add some comments though.

Please add this to the open commitfest so we don't lose track of it.

            regards, tom lane