--Schema
create table tbl2(id1 int, id2 varchar(10), id3 int);
create index idx2 on tbl2(id2, id3);

--Procedure to insert 1M data:

create or replace function insert_data(count1 int, count2 int) returns void
AS
$$
Begin
	for i IN 1..count1 loop
		insert into tbl2 values(i, 'a', i);
	end loop;	
	
	for i IN count1+1..count2 loop
		insert into tbl2 values(i, 'b', i);
	end loop;	
End;				  
$$	language plpgsql;

select insert_data(990000, 1000000);

--Procedure to select data 1000 times (1000 times selected to make data more appropriate.)
create or replace function select_data(count1 int) returns void
AS
$$
declare
	x int;
Begin
	for i IN 1..count1 loop
		select count(*) into x from tbl2 where id2>'a' and id3>990000; 
	end loop;	
End;				  
$$	language plpgsql;

select select_data(1000);

--Result:
				   Optimized		Original
Reading-1			2579.27			3621.82
Reading-2			2573.82			3618.29
Reading-3			2575.08			3625.16
Average				2576.06			3621.76

Overall Improvement					29%	

Instruction	Original Code took:	20057 M
Insrtuction	Optimized Code took: 	14557 M
So overall instruction improvement is around 27%.