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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 TYPE mytype AS ENUM ('x', 'y', 'z');
CREATE TABLE mytable (
id int,
type mytype
);
INSERT INTO mytable VALUES
(1, 'y'),
(1, 'x'),
(2, 'z');
SELECT * FROM mytable;
3 rows affected
| id | type |
|---|---|
| 1 | y |
| 1 | x |
| 2 | z |
SELECT DISTINCT ON (id)
id,
type
FROM mytable m
ORDER BY id, type
| id | type |
|---|---|
| 1 | x |
| 2 | z |