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Help with an interesting Postgres question: Why isn't an Index Only Scan used on a partition accessed via the parent table?.
create table "table"(email text,quantity int);
insert into "table"values
('email1',-2),
('email2',-1),
('email3',0),
('email4',1),
('email5',1),
('email6',1),
('person1@domain1.com',2),
('person1@domain1.com',4),
('person2@domain1.com',3)
returning *;
CREATE TABLE
| quantity | |
|---|---|
| email1 | -2 |
| email2 | -1 |
| email3 | 0 |
| email4 | 1 |
| email5 | 1 |
| email6 | 1 |
| person1@domain1.com | 2 |
| person1@domain1.com | 4 |
| person2@domain1.com | 3 |
INSERT 0 9
SELECT
AVG(quantity) AS avg_quantity,
email,
(SELECT PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY quantity) FROM "table")
FROM "table"
GROUP BY email
HAVING AVG(quantity) > (SELECT PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY quantity) FROM "table");
| avg_quantity | percentile_disc | |
|---|---|---|
| 3.0000000000000000 | person2@domain1.com | 1 |
| 3.0000000000000000 | person1@domain1.com | 1 |
SELECT 2
with _(median) as materialized (
SELECT PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY quantity) FROM "table")
SELECT AVG(quantity) AS avg_quantity,
email,
(SELECT median from _)
FROM "table"
GROUP BY email
HAVING AVG(quantity) > (SELECT median from _);
| avg_quantity | median | |
|---|---|---|
| 3.0000000000000000 | person2@domain1.com | 1 |
| 3.0000000000000000 | person1@domain1.com | 1 |
SELECT 2
SELECT AVG(quantity) AS avg_quantity,
email,
median
FROM "table"
,(SELECT PERCENTILE_DISC(0.5)WITHIN GROUP(ORDER BY quantity) FROM "table")
AS _(median)
GROUP BY email,median
HAVING AVG(quantity) > median;
| avg_quantity | median | |
|---|---|---|
| 3.0000000000000000 | person2@domain1.com | 1 |
| 3.0000000000000000 | person1@domain1.com | 1 |
SELECT 2
/*
WITH tmp AS(
SELECT
AVG(quantity) AS avg_quantity,
email
FROM "table"
GROUP BY email
HAVING AVG(quantity) > (SELECT PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY quantity) FROM "table" )
)
SELECT tmp.*, PERCENTILE_DISC(0.9) WITHIN GROUP (ORDER BY "table".quantity)
from tmp, "table"
*/