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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
INSERT 0 9
| student | subject | grade |
|---|---|---|
| Alice | Geography | 4 |
| Alice | History | 4.5 |
| Alice | Math | 4 |
| Bob | Geography | 3 |
| Bob | History | 3 |
| Bob | Math | 3.5 |
| Charlie | Geography | 4.5 |
| Charlie | History | 4 |
| Charlie | Math | 3 |
SELECT 9
| student | geography | history | math |
|---|---|---|---|
| Alice | 4 | 4.5 | 4 |
| Bob | 3 | 3 | 3.5 |
| Charlie | 4.5 | 4 | 3 |
SELECT 3
| student | name | value |
|---|---|---|
| Alice | subject | Geography |
| Alice | grade | 4 |
| Alice | subject | History |
| Alice | grade | 4.5 |
| Alice | subject | Math |
| Alice | grade | 4 |
| Bob | subject | Geography |
| Bob | grade | 3 |
| Bob | subject | History |
| Bob | grade | 3 |
| Bob | subject | Math |
| Bob | grade | 3.5 |
| Charlie | subject | Geography |
| Charlie | grade | 4.5 |
| Charlie | subject | History |
| Charlie | grade | 4 |
| Charlie | subject | Math |
| Charlie | grade | 3 |
SELECT 18