Horton

Re: making EXPLAIN extensible

Andrei Lepikhov <lepihov@gmail.com>

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From: Andrei Lepikhov <lepihov@gmail.com>
To: Sami Imseih <samimseih@gmail.com>, Robert Haas <robertmhaas@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Jeff Davis <pgsql@j-davis.com>, Thom Brown <thom@linux.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-03-19T20:37:23Z
Lists: pgsql-hackers

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Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. pg_overexplain: Use PG_MODULE_MAGIC_EXT.

  2. pg_overexplain: Call previous hooks as appropriate.

  3. pg_overexplain: Additional EXPLAIN options for debugging.

  4. Add an additional hook for EXPLAIN option validation.

  5. Add some new hooks so extensions can add details to EXPLAIN.

  6. Make it possible for loadable modules to add EXPLAIN options.

On 19/3/2025 18:41, Sami Imseih wrote:
>> On Wed, Mar 19, 2025 at 11:38 AM Sami Imseih <samimseih@gmail.com> wrote:
>>> ... as I made the hook signature match that of
>>> ParseExplainOptionList, so both pstate and the options list
>>> are now available to the hook.
>>
>> This version LGTM, except it's not pgindent-clean.
> 
> ugh, sorry about that. ran it for both modified files and it found one
> indentation correction from v2.
> 
>> index 1d4be3c18ac..8fe1ca5c73e 100644
> 38c38
> < +        (*explain_validate_options_hook) (es, options, pstate);
> ---
>> +        (*explain_validate_options_hook)(es, options, pstate);
> 59c59
> < 2.47.1
> 
> v3 attached.
I want to criticize this patch a bit. ;) Why do you think this hook is 
not redundant? May we avoid it at all? It seems to perform a too-narrow 
task.
For example, if you want to separate parameters that may be used on a 
plain EXPLAIN and on EXPLAIN ANALYZE to get behaviour like the following:

EXPLAIN (BUFFERS ON, TIMING ON) SELECT * FROM pg_class;
ERROR: EXPLAIN option TIMING requires ANALYZE

It would be better to add the parameter "type: EXPLAIN_ONLY | 
ANALYZE_ONLY | BOTH" to the RegisterExtensionExplainOption() routine. 
This value will be saved inside the ExplainExtensionOption structure and 
processed by the core inside the ParseExplainOptionList.

 > ERROR:  EXPLAIN options REMOTE_PLANS and ANALYZE cannot be used
 > together
I think the additional parameter covers the case you provided, isn't it?

-- 
regards, Andrei Lepikhov