Horton

Re: Missing comments/docs about custom scan path

Etsuro Fujita <etsuro.fujita@gmail.com>

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From: Etsuro Fujita <etsuro.fujita@gmail.com>
To: Richard Guo <guofenglinux@gmail.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2023-08-30T09:07:59Z
Lists: pgsql-hackers 
Hi Richard,

On Wed, Aug 30, 2023 at 11:05 AM Richard Guo <guofenglinux@gmail.com> wrote:
> 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.

Agreed.

I have committed the patch.  Thanks for taking a look!

Best regards,
Etsuro Fujita

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.