Horton

Re: making EXPLAIN extensible

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Sami Imseih <samimseih@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Andrei Lepikhov <lepihov@gmail.com>, Jeff Davis <pgsql@j-davis.com>, Thom Brown <thom@linux.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-03-21T18:37:05Z
Lists: pgsql-hackers

Commits

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.

Sami Imseih <samimseih@gmail.com> writes:
> overall this LGTM, and I don't really have other comments.

I took a look through v8, and have just a couple of trivial nits:

+static void overexplain_debug_handler(ExplainState *, DefElem *,
+                                      ParseState *);
+static void overexplain_range_table_handler(ExplainState *, DefElem *,
+                                            ParseState *);

I cordially hate this parameter-name-less style of function
declaration, and consider it Stroustrup's single worst idea in C++.
It rests on the assumption that parameter names convey zero
information, which is wrongheaded for any function more complex than,
say, addition.  Also, even if you like this style, clang-tidy probably
won't (cf for example 035ce1feb).

pgoverexplain.sgml seems to have been formatted to fit in about an
85-column window.  Please don't do that --- you might as well have
made it 99 columns wide or any other random number, it still looks
like heck in 80 columns.

Other than that, there's room to debate exactly what to show.
But as long as we're agreed that we won't hold this module to
high cross-version compatibility standards, that doesn't seem
like a problem.  I'm okay with this as a starting point.

			regards, tom lane