For loop execution times in PostgreSQL 12 vs 15

[Adithya Kumaranchath <akumaranchath@xxxxxxxx>]

Hi all,

I am running a simple test and am curious to know why a difference in execution times between PostgreSQL 12 vs PostgreSQL 15.

I have this function:

CREATE function test() returns int language plpgsql as $$
declare
      v_number bigint;
      v_multiplier float = 3.14159;
      loop_cnt bigint;
begin

      for loop_cnt in 1..1000000000
      loop
            v_number := 1000;
            v_number := v_number * v_multiplier;
      end loop;

      return 0;

end;$$;

I execute this in PostgreSQL 12:

PostgreSQL 15:

It is much faster in 15 than in 12, and while I love the performance improvement. I am curious to know the rationale behind this improvement on PostgreSQL 15.

The test result is from PostgreSQL on Windows but I observed the same behavior on Linux OS too.

Server Spec:

Intel i7-8650U CPU @1.90GHz 2.11GHz

RAM 16 GB

Windows 11 Enterprise

Thanks,
Adi