Re: Oversight in reparameterize_path_by_child leading to executor crash

On 23/8/2023 12:37, Richard Guo wrote:
> To fix it we may need to modify RelOptInfos for Path, BitmapHeapPath,
> ForeignPath and CustomPath, and modify IndexOptInfos for IndexPath.  It
> seems that that is not easily done without postponing reparameterization
> of paths until createplan.c.
>
> Attached is a patch which is v5 + fix for this new issue.

Having looked into the patch for a while, I couldn't answer to myself
for some stupid questions:

1. If we postpone parameterization until the plan creation, why do we
still copy the path node in the FLAT_COPY_PATH macros? Do we really need it?

2. I see big switches on path nodes. May it be time to create a
path_walker function? I recall some thread where such a suggestion was
declined, but I don't remember why.

3. Clause changing is postponed. Why does it not influence the
calc_joinrel_size_estimate? We will use statistics on the parent table
here. Am I wrong?