By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
Help with an interesting Postgres question: Why isn't an Index Only Scan used on a partition accessed via the parent table?.
create table random_values(id int);
CREATE TABLE
truncate random_values;
insert into random_values (SELECT
values.value
FROM (
SELECT
-- 10000 here is parts which represent 100 by extrapoliated
FLOOR(random() * 10000) AS random_value
FROM
-- here the end is the number of values needed to generate.
generate_series(1,1000000) i
) x,
( VALUES
(1, 0, 7500), (2, 7501, 9000), (3, 9001, 9500),
(4, 9501, 9800), (5, 9801, 10000)
) AS values (value, strt, ending)
WHERE
x.random_value BETWEEN values.strt AND values.ending
);
TRUNCATE TABLE
INSERT 0 1000000
select *,(count(*)*1.0/1000000)::float from random_values group by 1 order by 1;
| id | float8 |
|---|---|
| 1 | 0.750275 |
| 2 | 0.149736 |
| 3 | 0.05017 |
| 4 | 0.029985 |
| 5 | 0.019834 |
SELECT 5