Re: Missing comments/docs about custom scan path

On Thu, Aug 3, 2023 at 6:01 PM Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com> wrote:
> On Mon, Jul 31, 2023 at 7:05 PM Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com> wrote:
> > While working on [1], I noticed $SUBJECT:

Another thing I would like to propose is minor adjustments to the docs
related to parallel query:

A custom scan provider will typically add paths for a base relation by
setting the following hook, which is called after the core code has
generated all the access paths it can for the relation (except for
Gather paths, which are made after this call so that they can use
partial paths added by the hook):

For clarity, I think "except for Gather paths" should be "except for
Gather and Gather Merge paths".

Although this hook function can be used to examine, modify, or remove
paths generated by the core system, a custom scan provider will
typically confine itself to generating CustomPath objects and adding
them to rel using add_path.

For clarity, I think "adding them to rel using add_path" should be eg,
"adding them to rel using add_path, or using add_partial_path if they
are partial paths".

Attached is a patch for that.

Best regards,
Etsuro Fujita