Re: Hooking into ExplainOneQuery() complicated by missing standard_ExplainOneQuery

On Mon, Mar 04, 2024 at 03:41:16PM +0300, Aleksander Alekseev wrote:
>> I wanted to hook into the EXPLAIN output for queries and add some
>> extra information, but since there is no standard_ExplainOneQuery() I
>> had to copy the code and create my own version.
>>
>> Since the pattern with other hooks for a function
>> WhateverFunction() seems to be that there is a
>> standard_WhateverFunction() for each WhateverFunction_hook, I
>> created a patch to follow this pattern for your consideration.

So you've wanted to be able to add some custom information at the end
or the beginning of ExplainState's output buffer, before falling back
to the in-core path. What was the use case, if I may ask?

>> I was also considering adding a callback so that you can annotate
>> any node with explanatory information that is not a custom scan
>> node. This could be used to propagate and summarize information
>> from custom scan nodes, but I had no immediate use for that so did
>> not add it here. I would still be interested in hearing if you
>> think this is something that would be useful to the community.

That depends.

> I registered the patch on the nearest open CF [1] and marked it as
> RfC. It is a pretty straightforward refactoring.
>
> [1]: https://commitfest.postgresql.org/48/4879/

I know that we're in the middle of commit fest 47 while this is in 48,
but I can't really see a reason why we should not do that earlier than
v18. One point about core is to be flexible for extension code. So I\
have no objections, others are free to comment.
--
Michael