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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