Re: Max connections reached without max connections reached

[James Sewell <james.sewell@xxxxxxxxxxxx>]

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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