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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 t (person text, persons_mother text);
INSERT INTO t VALUES
('Becky','Not in list'),
('Sally','Becky'),
('Libby','Sally'),
('Millie','Sally'),
('Sharon','Libby');
5 rows affected
SELECT person,persons_mother,
COALESCE((SELECT string_agg(t2.person,',')
FROM t t2
WHERE t1.person = t2.persons_mother),'N/A')
FROM t t1;
| person | persons_mother | coalesce |
|---|---|---|
| Becky | Not in list | Sally |
| Sally | Becky | Libby,Millie |
| Libby | Sally | Sharon |
| Millie | Sally | N/A |
| Sharon | Libby | N/A |