Re: PG 15 (and to a smaller degree 14) regression due to ExprEvalStep size

Hi,

On 2023-02-23 13:56:56 -0500, Tom Lane wrote:
> Corey Huinker  writes:
> > My not-ready-for-16 work on CAST( ... ON DEFAULT ... ) involved making
> > FuncExpr/IoCoerceExpr/ArrayCoerceExpr have a safe_mode flag, and that
> > necessitates adding a reserror boolean to ExprEvalStep for subsequent steps
> > to test if the error happened.
> 
> Why do you want it in ExprEvalStep ... couldn't it be in ExprState?
> I can't see why you'd need more than one at a time during evaluation.

I don't know exactly what CAST( ... ON DEFAULT ... ) is aiming for - I guess
it wants to assign a different value when the cast fails?  Is the default
expression a constant, or does it need to be runtime evaluated?  If a const,
then the cast steps just could assign the new value. If runtime evaluation is
needed I'd expect the various coerce steps to jump to the value implementing
the default expression in case of a failure.

So I'm not sure we even need a reserror field in ExprState.

Greetings,

Andres Freund