Postgres 10

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?.
select version();


version


PostgreSQL 10.12 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.3.1 20190507 (Red Hat 8.3.1-4), 64-bit


CREATE TABLE users (
  user_id INT PRIMARY KEY,
  name CHARACTER VARYING(50)
);

CREATE TABLE orders_catalog (
	order_code INT PRIMARY KEY,
	order_desc CHARACTER VARYING(50) NOT NULL,
	cost REAL NOT NULL
);

CREATE TABLE encounter (
	encounter_id INT PRIMARY KEY,
	user_id INT NOT NULL,
	encounter_type CHARACTER VARYING(50) NOT NULL,

	CONSTRAINT FK_encounter FOREIGN KEY (user_id) REFERENCES users(user_id)
);

CREATE TABLE orders (
	order_id INT PRIMARY KEY,
	order_code INT NOT NULL,
	encounter_id INT NOT NULL,
	created_dt TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,

	CONSTRAINT FK_orders_catalog FOREIGN KEY (order_code) REFERENCES orders_catalog (order_code),
	CONSTRAINT FK_orders_encounter FOREIGN KEY (encounter_id) REFERENCES encounter(encounter_id)
);
--

INSERT INTO users(user_id, name) VALUES(1, 'Peter');
INSERT INTO users(user_id, name) VALUES(2, 'Charles');
INSERT INTO users(user_id, name) VALUES(3, 'Eva') ;
INSERT INTO users(user_id, name) VALUES(4, 'John');
INSERT INTO users(user_id, name) VALUES(5, 'Helene');

INSERT INTO orders_catalog(order_code, order_desc, cost) VALUES (10000, 'Painting', 100.34);
INSERT INTO orders_catalog(order_code, order_desc, cost) VALUES (10001, 'Painting', 214.11);
INSERT INTO orders_catalog(order_code, order_desc, cost) VALUES (10002, 'Painting', 214.11);
INSERT INTO orders_catalog(order_code, order_desc, cost) VALUES (10003, 'Spare part', 181.03);
INSERT INTO orders_catalog(order_code, order_desc, cost) VALUES (10004, 'Sheet metal', 168.18);
INSERT INTO orders_catalog(order_code, order_desc, cost) VALUES (10005, 'Sheet metal', 240.02);
INSERT INTO orders_catalog(order_code, order_desc, cost) VALUES (10006, 'Sheet metal', 240.02);
INSERT INTO orders_catalog(order_code, order_desc, cost) VALUES (10007, 'Electricity', 146.85);
INSERT INTO orders_catalog(order_code, order_desc, cost) VALUES (10008, 'Spare part', 162.13);
INSERT INTO orders_catalog(order_code, order_desc, cost) VALUES (10009, 'Electricity', 140.02);
INSERT INTO orders_catalog(order_code, order_desc, cost) VALUES (10010, 'Electricity', 180.02);

INSERT INTO encounter(encounter_id, user_id, encounter_type) VALUES(100,1,'appointment');
INSERT INTO encounter(encounter_id, user_id, encounter_type) VALUES(101,2,'appointment');
INSERT INTO encounter(encounter_id, user_id, encounter_type) VALUES(102,3,'appointment');
INSERT INTO encounter(encounter_id, user_id, encounter_type) VALUES(103,4,'urgent');
INSERT INTO encounter(encounter_id, user_id, encounter_type) VALUES(104,5,'urgent');
INSERT INTO encounter(encounter_id, user_id, encounter_type) VALUES(105,1,'appointment');
INSERT INTO encounter(encounter_id, user_id, encounter_type) VALUES(106,2,'appointment');
INSERT INTO encounter(encounter_id, user_id, encounter_type) VALUES(107,3,'waiting');
INSERT INTO encounter(encounter_id, user_id, encounter_type) VALUES(108,4,'urgent');
INSERT INTO encounter(encounter_id, user_id, encounter_type) VALUES(109,5,'waiting');
INSERT INTO encounter(encounter_id, user_id, encounter_type) VALUES(110,1,'waiting');

INSERT INTO orders(order_id, order_code, encounter_id, created_dt) VALUES (1000,10000,100,'2009-06-16 09:12');
INSERT INTO orders(order_id, order_code, encounter_id, created_dt) VALUES (1001,10001,101,'2009-06-16 09:12');
INSERT INTO orders(order_id, order_code, encounter_id, created_dt) VALUES (1002,10002,102,'2009-06-16 09:12');
INSERT INTO orders(order_id, order_code, encounter_id, created_dt) VALUES (1003,10003,103,'2009-12-03 09:50');
INSERT INTO orders(order_id, order_code, encounter_id, created_dt) VALUES (1004,10004,104,'2010-02-24 12:21');
INSERT INTO orders(order_id, order_code, encounter_id, created_dt) VALUES (1005,10005,105,'2010-03-27 23:54');
INSERT INTO orders(order_id, order_code, encounter_id, created_dt) VALUES (1006,10006,106,'2010-03-22 12:43');
INSERT INTO orders(order_id, order_code, encounter_id, created_dt) VALUES (1007,10007,107,'2010-02-24 12:21');
INSERT INTO orders(order_id, order_code, encounter_id, created_dt) VALUES (1008,10008,108,'2010-03-04 08:55');
INSERT INTO orders(order_id, order_code, encounter_id, created_dt) VALUES (1009,10009,109,'2010-03-06 09:25');
INSERT INTO orders(order_id, order_code, encounter_id, created_dt) VALUES (1010,10010,110,'2010-03-22 11:18');

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

1 rows affected

SELECT
  u.user_id,
  name,
  COUNT (e.encounter_type) OVER (
    PARTITION BY u.user_id
  ) AS position,
  SUM (c.cost) OVER (
    PARTITION BY o.encounter_id ORDER BY o.created_dt DESC
  ) AS cost
FROM
  users u
INNER JOIN
  encounter e USING (user_id)
INNER JOIN
  orders o USING (encounter_id)
INNER JOIN
  orders_catalog c USING (order_code)
ORDER BY user_id;


user_id
name
position
cost


1
Peter
3
180.02

1
Peter
3
240.02

1
Peter
3
100.34

2
Charles
2
240.02

2
Charles
2
214.11

3
Eva
2
214.11

3
Eva
2
146.85

4
John
2
181.03

4
John
2
162.13

5
Helene
2
168.18

5
Helene
2
140.02
user_id	name	position	cost
1	Peter	3	180.02
1	Peter	3	240.02
1	Peter	3	100.34
2	Charles	2	240.02
2	Charles	2	214.11
3	Eva	2	214.11
3	Eva	2	146.85
4	John	2	181.03
4	John	2	162.13
5	Helene	2	168.18
5	Helene	2	140.02