>
>
> I'm guessing this won't be back-patched? Is it possible to somehow read
> this information from a C function?
>
>

Ok it is possible, I've got a C extension up and running which hooks
ExecutorStart, then once for each TX ( I monitor the nesting depth like in
pg_stat_statements, and only attach at the top level) attaches a sub
transaction callback, tracking start subtransaction events and incrementing
a counter / keeping track of the worst offenders in a hashmap.

This seems to work very well - but I've got a question. How many sub
transactions would you expect the following anon block and function to
create respectively? The first seems to report 9, and the second 10 - is
this expected? It feels like it might be - I just want to make sure.

do $$
begin
   for counter in 1..10 loop
   begin
   INSERT INTO a VALUES (counter);
exception
when no_data_found then  raise exception 'gosh';
  end;
   end loop;
end;
$$


CREATE OR REPLACE FUNCTION public.create_subtransactions()
 RETURNS void
 LANGUAGE plpgsql
AS $function$
begin
   for counter in 1..10 loop
     begin
       INSERT INTO a VALUES (counter);
     exception
       when no_data_found then  raise exception 'gosh';
     end;
  end loop;
end;
$function$

- James

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