Re: Using Expanded Objects other than Arrays from plpgsql

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

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Pavel Borisov <pashkin.elfe@gmail.com>
Cc: Michel Pelletier <pelletier.michel@gmail.com>, Andrey Borodin <x4mmm@yandex-team.ru>, Pavel Stehule <pavel.stehule@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2025-02-03T17:53:06Z
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. Allow extension functions to participate in in-place updates.

  2. Implement new optimization rule for updates of expanded variables.

  3. Detect whether plpgsql assignment targets are "local" variables.

  4. Preliminary refactoring of plpgsql expression construction.

  5. Refactor pl_funcs.c to provide a usage-independent tree walker.

  6. Generalize plpgsql's heuristic for importing expanded objects.

Pavel Borisov <pashkin.elfe@gmail.com> writes:
> Minor notes on the patches:

> If dump_* functions could use the newly added walker, the code would
> look better. I suppose the main complication is that dump_* functions
> contain a lot of per-statement prints/formatting. So maybe a way to
> implement this is to put these statements into the existing tree
> walker i.e. plpgsql_statement_tree_walker_impl() and add an argument
> bool dump_debug into it. So in effect called with dump_debug=false
> plpgsql_statement_tree_walker_impl() would walk silent, and with
> dump_debug=false it would walk and print what is supposed to be
> printed currently in dump_* functions. Maybe there are other problems
> besides this?

I'm not thrilled with that idea, mainly because it would add overhead
to the performance-relevant cases (mark and free) to benefit a rarely
used debugging feature.  I'm content to leave the debug code out of
this for now --- it seems to me that it's serving a different master
and doesn't have to be unified with the other routines.

> For exec_check_rw_parameter():

> I think renaming expr->expr_simple_expr to sexpr saves few bytes but
> doesn't makes anything simpler, so if possible I'd prefer using just
> expr->expr_simple_expr with necessary casts. Furtermore in this
> function mostly we use cast results fexpr, opexpr and sbsref of
> expr->expr_simple_expr that already has separate names.

Hmm, I thought it looked cleaner like this, but I agree beauty
is in the eye of the beholder.  Anybody else have a preference?

> Transferring target param as int paramid looks completely ok. But we
> have unconditional checking Assert(paramid == expr->target_param + 1),
> so it looks as a redundant split as of now. Do we plan a true split
> and removal of this assert in the future?

We've already fetched the target variable using the paramid (cf
plpgsql_param_eval_var_check), so I think checking that the
expression does match it seems like a useful sanity check.
Agreed, it shouldn't ever not match, but that's why that's just
an Assert.

> Thanks for creating and working on this patch!

Thanks for reviewing it!

			regards, tom lane