Re: enhancing plpgsql debug api - hooks on statements errors and function errors - Mailing list pgsql-hackers

From Kirk Wolak
Subject Re: enhancing plpgsql debug api - hooks on statements errors and function errors
Date
Msg-id CACLU5mS15U7ch3ZkQ4rc0Mrw-1xgX6fPRKeX28wP7xtg=v7mGg@mail.gmail.com
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In response to Re: enhancing plpgsql debug api - hooks on statements errors and function errors  (Pavel Stehule <pavel.stehule@gmail.com>)
List pgsql-hackers
On Tue, Apr 25, 2023 at 11:33 AM Pavel Stehule <pavel.stehule@gmail.com> wrote:
Hi
út 25. 4. 2023 v 10:27 odesílatel Pavel Stehule <pavel.stehule@gmail.com> napsal:
Hi

When I implemented profiler and coverage check to plpgsql_check I had to write a lot of hard maintaining code related to corect finishing some operations (counter incrementing) usually executed by stmt_end and func_end hooks. It is based on the fmgr hook and its own statement call stack. Can be nice if I can throw this code and use some nice buildin API.

Can we enhance dbg API with two hooks stmt_end_err func_end_err ?

These hooks can be called from exception handlers before re raising.

Or we can define new hooks like executor hooks - stmt_exec and func_exec. In custom hooks the exception can be catched.

What do you think about this proposal?

+1.  I believe I bumped into a few of these use cases with plpgsql_check (special handling for security definer and exception handling).
  My cursory review of the patch file is that despite the movement of the code, it feels pretty straight forward.

The 7% overhead appears in a "tight loop", so it's probably really overstated.  I will see if I can apply this and do a more realistic test.
[I have a procedure that takes ~2hrs to process a lot of data, I would be curious to see this impact and report back] 
 
I did quick and ugly benchmark on worst case

CREATE OR REPLACE FUNCTION public.speedtest(i integer)
 RETURNS void
 LANGUAGE plpgsql
 IMMUTABLE
AS $function$
declare c int = 0;
begin
  while c < i
  loop
    c := c + 1;
  end loop;
  raise notice '%', c;
end;
$function$

and is possible to write some code (see ugly patch) without any performance impacts if the hooks are not used. When hooks are active, then there is 7% performance lost. It is not nice - but this is the worst case. The impact on real code should be significantly lower

Regards

Pavel

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