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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?.
| date | quarter |
|---|---|
| 2021-01-01 00:00:00 | 2020-12-01 00:00:00 |
| 2021-02-01 00:00:00 | 2020-12-01 00:00:00 |
| 2021-03-01 00:00:00 | 2021-03-01 00:00:00 |
| 2021-04-01 00:00:00 | 2021-03-01 00:00:00 |
| 2021-05-01 00:00:00 | 2021-03-01 00:00:00 |
| 2021-06-01 00:00:00 | 2021-06-01 00:00:00 |
| 2021-07-01 00:00:00 | 2021-06-01 00:00:00 |
| 2021-08-01 00:00:00 | 2021-06-01 00:00:00 |
| 2021-09-01 00:00:00 | 2021-09-01 00:00:00 |
| 2021-10-01 00:00:00 | 2021-09-01 00:00:00 |
| 2021-11-01 00:00:00 | 2021-09-01 00:00:00 |
| 2021-12-01 00:00:00 | 2021-12-01 00:00:00 |
SELECT 12