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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(t_id int);
insert into t values (1),(2),(3),(4);
create table u(u_id int);
insert into u values (5),(6),(7);
create table v(v_id int);
CREATE TABLE
INSERT 0 4
CREATE TABLE
INSERT 0 3
CREATE TABLE
select * from t,u
| t_id | u_id |
|---|---|
| 1 | 5 |
| 1 | 6 |
| 1 | 7 |
| 2 | 5 |
| 2 | 6 |
| 2 | 7 |
| 3 | 5 |
| 3 | 6 |
| 3 | 7 |
| 4 | 5 |
| 4 | 6 |
| 4 | 7 |
SELECT 12
select * from t FULL OUTER JOIN u ON FALSE
| t_id | u_id |
|---|---|
| null | 5 |
| null | 6 |
| null | 7 |
| 1 | null |
| 2 | null |
| 3 | null |
| 4 | null |
SELECT 7
select * from t,v
| t_id | v_id |
|---|
SELECT 0
select * from t FULL OUTER JOIN v ON FALSE
| t_id | v_id |
|---|---|
| 1 | null |
| 2 | null |
| 3 | null |
| 4 | null |
SELECT 4