Horton

Re: Missing comments/docs about custom scan path

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Etsuro Fujita <etsuro.fujita@gmail.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2023-08-30T02:05:24Z
Lists: pgsql-hackers 
On Tue, Aug 29, 2023 at 5:08 PM Etsuro Fujita <etsuro.fujita@gmail.com>
wrote:

> 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".


+1.  I can see that this change makes the doc more consistent with the
comments in set_rel_pathlist.

Thanks
Richard

Commits

  1. Doc: Improve documentation for creating custom scan paths.

  2. Doc: update documentation for creating custom scan paths.

  3. Update comments on CustomPath struct.

  4. Basic partition-wise join functionality.

  5. Allow FDWs and custom scan providers to replace joins with scans.