Re: Rethinking plpgsql's assignment implementation

Hi

I checked a performance and it looks so access to record's field is faster,
but an access to arrays field is significantly slower

do $$
declare
a int[];
aux int;
rep boolean default true;
begin
for i in 1..5000
loop
a[i]:= 5000 - i;
end loop;

raise notice '%', a[1:10];

while rep
loop
rep := false;
for i in 1..5000
loop
if a[i] > a[i+1] then
aux := a[i];
a[i] := a[i+1]; a[i+1] := aux;
rep := true;
end if;
end loop;
end loop;

raise notice '%', a[1:10];

end;
$$;

This code is about 3x slower than master (40 sec x 12 sec). I believe so
this is a worst case scenario

I tested pi calculation

CREATE OR REPLACE FUNCTION pi_est_1(n int)
RETURNS numeric AS $$
DECLARE
accum double precision DEFAULT 1.0;
c1 double precision DEFAULT 2.0;
c2 double precision DEFAULT 1.0;
BEGIN
FOR i IN 1..n
LOOP
accum := accum * ((c1 * c1) / (c2 * (c2 + 2.0)));
c1 := c1 + 2.0;
c2 := c2 + 2.0;
END LOOP;
RETURN accum * 2.0;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION pi_est_2(n int)
RETURNS numeric AS $$
DECLARE
accum double precision DEFAULT 1.0;
c1 double precision DEFAULT 2.0;
c2 double precision DEFAULT 1.0;
BEGIN
FOR i IN 1..n
LOOP
accum := accum * ((c1 * c1) / (c2 * (c2 + double precision '2.0')));
c1 := c1 + double precision '2.0';
c2 := c2 + double precision '2.0';
END LOOP;
RETURN accum * double precision '2.0';
END;
$$ LANGUAGE plpgsql;

And the performance is 10% slower than on master

Interesting point - the master is about 5% faster than pg13