Re: Behavior of PL/pgSQL function following drop and re-create of a table that it uses

On Tue, Mar 7, 2023 at 9:49 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> "David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> > So I found where this difference in behavior is at least explicitly
> noted:
>
> >/*
> > * If it's a named composite type (or domain over one), find the typcache
> > * entry and record the current tupdesc ID, so we can detect changes
> > * (including drops). We don't currently support on-the-fly replacement
> > * of non-composite types, else we might want to do this for them too.
> > */
>
> I'm not quite sure that that's related, really. That code is concerned
> with detecting changes to an already-identified type (that is, type
> OID NNN has different details now than it did before). It seemed to
> me that Bryn's question was more about reacting to cases where a given
> string of source code would resolve to a different type OID than it
> did a moment ago.

Sorta, and now I see why %TYPE doesn't work but %ROWTYPE does - a change in
the former is necessarily a new OID while a change to the later will have
the same OID but a different internal structure that the type reference
compiled into the function can leverage to be resolve its structure at
runtime.

Of course, I went from almost clueless to this answer in just over an hour
so it is possible I'm wrong. But it seems to fit so far.

David J.