## Tuesday, March 5, 2024

### How fast is plpgsql?

Ten years ago I did some speed tests of plpgsql. I did same tests on same computer, and now, the plpgsql is about 3-4 times faster. There is still significant overhead against native (without plpgsql function) query, but it is reduced (little bit). I would to compare again with Python

```create table foo(a int, b int, c int, d int, e int);
insert into foo select random()*100, random()*100, random()*100, random()*100, random()*100 from generate_series(1,100000);

CREATE OR REPLACE FUNCTION public.myleast1(VARIADIC integer[])
RETURNS integer LANGUAGE plpgsql IMMUTABLE STRICT
AS \$function\$
declare result int;
a int;
begin
foreach a in array \$1
loop
if result is null then
result := a;
elseif a < result then
result := a;
end if;
end loop;
return result;
end;
\$function\$;

CREATE OR REPLACE FUNCTION public.myleast6(VARIADIC a integer[])
RETURNS integer LANGUAGE plpython3u IMMUTABLE STRICT
AS \$function\$
r = None
for x in a:
if r is None or x < r:
r = x
return r
\$function\$;

(2024-03-05 12:25:10) postgres=# select count(*) filter (where a = least(a,b,c,d,e)) from foo;
┌───────┐
│ count │
╞═══════╡
│ 20544 │
└───────┘
(1 row)

Time: 15,265 ms
(2024-03-05 12:25:53) postgres=# select count(*) filter (where a = myleast1(a,b,c,d,e)) from foo;
┌───────┐
│ count │
╞═══════╡
│ 20544 │
└───────┘
(1 row)

Time: 221,726 ms
(2024-03-05 12:25:59) postgres=# select count(*) filter (where a = myleast6(a,b,c,d,e)) from foo;
┌───────┐
│ count │
╞═══════╡
│ 20544 │
└───────┘
(1 row)

Time: 282,732 ms
```

Ten years ago plpgsql was about 30% slower, now it is about 20% faster.

Attention - this benchmark is pretty unrealistic - the best benefit of stored procedures is when they are used like glue of SQL statements. On second hand, can be interesting to know the overhead of stored procedures against native C implementation - this is like worst case.