> On Mon, Nov 30, 2020 at 02:26:19PM +0100, Dmitry Dolgov wrote:
> > On Mon, Nov 30, 2020 at 04:12:29PM +0300, Alexander Korotkov wrote:
> >
> > > > My first question is whether we're
> > > > able to handle different subscript types differently. For instance,
> > > > one day we could handle jsonpath subscripts for jsonb. And for sure,
> > > > jsonpath subscripts are expected to be handled differently from text
> > > > subscripts. I see we can distinguish types during in prepare and
> > > > validate functions. But it seems there is no type information in
> > > > fetch and assign functions. Should we add something like this to the
> > > > SubscriptingRefState for future usage?
> > > >
> > > > Datum uppertypeoid[MAX_SUBSCRIPT_DEPTH];
> > > > Datum lowertypeoid[MAX_SUBSCRIPT_DEPTH];
> > >
> > > Yes, makes sense. My original idea was that it could be done within the
> > > jsonpath support patch itself, but at the same time providing these
> > > fields into SubscriptingRefState will help other potential extensions.
> > >
> > > Having said that, maybe it would be even better to introduce a field
> > > with an opaque structure for both SubscriptingRefState and
> > > SubscriptingRef, where every implementation of custom subscripting can
> > > store any necessary information? In case of jsonpath it could keep type
> > > information acquired in prepare function, which would be then passed via
> > > SubscriptingRefState down to the fetch/assign.
> >
> > The idea of an opaque field in SubscriptingRef structure is more
> > attractive to me. Could you please implement it?
>
> Sure, doesn't seem to be that much work.
The attached implementation should be enough I guess, as fetch/assign
are executed in a child memory context of one where prepare does the
stuff.