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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 (id int primary key not null, a int);
CREATE TABLE
insert into t (id, a) values (1, 100), (2, 200), (3, 260);
INSERT 0 3
select * from t;
| id | a |
|---|---|
| 1 | 100 |
| 2 | 200 |
| 3 | 260 |
SELECT 3
select id, a from t group by id
| id | a |
|---|---|
| 2 | 200 |
| 3 | 260 |
| 1 | 100 |
SELECT 3
select id, a from t group by a
ERROR: column "t.id" must appear in the GROUP BY clause or be used in an aggregate function LINE 1: select id, a from t group by a ^