Re: A very quick observation of dangling pointers in Postgres pathlists

On Tue, 21 Apr 2026 at 20:54, Andrei Lepikhov <lepihov(at)gmail(dot)com> wrote:
>
> On 21/04/2026 10:35, David Rowley wrote:
> > IMO, we should write a function like copy_path() or reparent_path(),
> > which creates a copy of the given Path, or the latter also would copy
> > then set the ->parent to the given RelOptInfo. Any time we use a path
> > directly from the pathlist of another RelOptInfo, we should reparent
> > or copy it. We could add an Assert in add_path() to check the new path
> > has the correct parent to help us find the places where we forget to
> > do this.
>
> It would be great to have a copy_path() function. At the moment, I create a
> limited version each time in an extension module, using
> reparameterize_path_by_child as a guide since it ensures the core can handle
> path copies.
> Do you mean we can introduce such a copy routine to fix current issue? Here is
> the problem: dangling pointers are detected only by external tools. I can't
> imagine an SQL reproducer to test this machinery.

I had anticipated that we'd only fix in master as we'd probably need a
new callback in CustomPathMethods.

David