Re: Subplan result caching

On 2018-05-23 12:51:38 -0400, Tom Lane wrote:
> Heikki Linnakangas <hlinnaka@iki.fi> writes:
> > On 23/05/18 19:25, Tom Lane wrote:
> >> To make this
> >> patch safe, I think you'd need to grovel through the subquery and make
> >> sure that the parameters are only used as inputs to operators that belong
> >> to the type's default btree or hash opfamily.  (Many other cases would
> >> work in practice, but we have no semantic knowledge that would let us be
> >> sure of that.)
> 
> > Hmm. First thing that comes to mind is to use the raw bytes as cache 
> > key, only treating Datums as equal if their binary representation is 
> > identical.
> 
> Ah.  That would work, though it'd make the number of subquery executions
> even less predictable (since some logically-equal values would compare
> as physically unequal).

As long as there's no volatile functions, would anybody care?

Greetings,

Andres Freund