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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 0 100
| done | grp |
|---|---|
| 2022-11-14 19:13:20.552985 | 0 |
| 2022-11-14 19:15:15.903866 | 0 |
| 2022-11-14 19:16:52.406207 | 0 |
| 2022-11-14 19:18:25.09944 | 0 |
| 2022-11-14 19:19:04.792935 | 0 |
| 2022-11-14 19:20:35.392931 | 0 |
| 2022-11-14 19:22:58.484016 | 1 |
| 2022-11-14 19:23:57.692733 | 1 |
| 2022-11-14 19:25:39.628439 | 1 |
| 2022-11-14 19:27:02.214525 | 1 |
| 2022-11-14 19:28:56.145188 | 1 |
| 2022-11-14 19:30:09.047729 | 1 |
| 2022-11-14 19:31:04.276444 | 1 |
| 2022-11-14 19:32:58.515729 | 1 |
| 2022-11-14 19:34:44.854868 | 1 |
| 2022-11-14 19:36:05.97905 | 1 |
| 2022-11-14 19:37:49.897782 | 1 |
| 2022-11-14 19:39:04.917904 | 1 |
| 2022-11-14 19:40:39.342219 | 1 |
| 2022-11-14 19:42:16.607263 | 1 |
| 2022-11-14 19:43:24.444555 | 1 |
| 2022-11-14 19:45:06.99275 | 1 |
| 2022-11-14 19:46:17.042374 | 1 |
| 2022-11-14 19:47:32.300325 | 1 |
| 2022-11-14 19:49:19.034442 | 1 |
| 2022-11-14 19:50:55.119869 | 1 |
| 2022-11-14 19:52:33.383196 | 1 |
| 2022-11-14 19:53:31.799486 | 1 |
| 2022-11-14 19:55:16.318991 | 1 |
| 2022-11-14 19:57:08.507617 | 1 |
| 2022-11-14 19:58:38.427286 | 1 |
| 2022-11-14 20:00:07.55484 | 1 |
| 2022-11-14 20:01:25.094347 | 1 |
| 2022-11-14 20:03:01.516357 | 1 |
| 2022-11-14 20:04:33.337143 | 1 |
| 2022-11-14 20:06:00.570146 | 1 |
| 2022-11-14 20:07:37.592152 | 1 |
| 2022-11-14 20:09:02.504023 | 1 |
| 2022-11-14 20:10:58.945743 | 1 |
| 2022-11-14 20:11:47.903455 | 1 |
| 2022-11-14 20:13:05.401413 | 1 |
| 2022-11-14 20:15:25.773795 | 2 |
| 2022-11-14 20:16:57.634048 | 2 |
| 2022-11-14 20:17:40.360721 | 2 |
| 2022-11-14 20:19:24.972388 | 2 |
| 2022-11-14 20:21:13.17178 | 2 |
| 2022-11-14 20:22:47.022635 | 2 |
| 2022-11-14 20:23:45.553034 | 2 |
| 2022-11-14 20:25:18.772548 | 2 |
| 2022-11-14 20:26:57.047718 | 2 |
| 2022-11-14 20:28:02.843161 | 2 |
| 2022-11-14 20:30:13.899968 | 3 |
| 2022-11-14 20:31:04.723332 | 3 |
| 2022-11-14 20:32:50.568399 | 3 |
| 2022-11-14 20:34:46.883156 | 3 |
| 2022-11-14 20:35:54.440638 | 3 |
| 2022-11-14 20:37:46.371132 | 3 |
| 2022-11-14 20:38:50.949216 | 3 |
| 2022-11-14 20:40:26.922987 | 3 |
| 2022-11-14 20:41:33.372987 | 3 |
| 2022-11-14 20:43:00.139697 | 3 |
| 2022-11-14 20:44:36.033138 | 3 |
| 2022-11-14 20:46:41.610691 | 4 |
| 2022-11-14 20:47:55.916909 | 4 |
| 2022-11-14 20:49:38.232358 | 4 |
| 2022-11-14 20:50:45.630698 | 4 |
| 2022-11-14 20:52:57.169919 | 5 |
| 2022-11-14 20:53:46.507374 | 5 |
| 2022-11-14 20:55:48.817586 | 6 |
| 2022-11-14 20:57:26.798526 | 6 |
| 2022-11-14 20:58:35.093694 | 6 |
| 2022-11-14 21:00:24.901862 | 6 |
| 2022-11-14 21:01:53.255185 | 6 |
| 2022-11-14 21:03:03.410605 | 6 |
| 2022-11-14 21:04:05.945447 | 6 |
| 2022-11-14 21:05:48.910437 | 6 |
| 2022-11-14 21:07:17.26525 | 6 |
| 2022-11-14 21:09:23.650946 | 7 |
| 2022-11-14 21:10:35.146335 | 7 |
| 2022-11-14 21:12:06.720662 | 7 |
| 2022-11-14 21:13:21.381528 | 7 |
| 2022-11-14 21:15:08.67236 | 7 |
| 2022-11-14 21:16:21.303493 | 7 |
| 2022-11-14 21:17:56.787724 | 7 |
| 2022-11-14 21:18:59.923623 | 7 |
| 2022-11-14 21:20:38.869514 | 7 |
| 2022-11-14 21:22:51.911226 | 8 |
| 2022-11-14 21:24:16.977619 | 8 |
| 2022-11-14 21:25:30.501594 | 8 |
| 2022-11-14 21:26:49.517077 | 8 |
| 2022-11-14 21:28:51.033471 | 9 |
| 2022-11-14 21:30:01.324155 | 9 |
| 2022-11-14 21:31:26.233078 | 9 |
| 2022-11-14 21:33:03.327026 | 9 |
| 2022-11-14 21:34:57.923928 | 9 |
| 2022-11-14 21:35:35.148301 | 9 |
| 2022-11-14 21:37:49.640588 | 10 |
| 2022-11-14 21:39:25.776711 | 10 |
| 2022-11-14 21:40:22.338539 | 10 |
| 2022-11-14 21:42:09.141038 | 10 |
SELECT 100