Postgres 13

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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 t1 (pk integer NOT NULL PRIMARY KEY);
CREATE TABLE t2 (fk integer NOT NULL REFERENCES t1);
INSERT INTO t1 VALUES (1), (2);
INSERT INTO t2 VALUES (1);
2 rows affected

1 rows affected

SELECT *
FROM t1
LEFT JOIN t2
    ON t2.fk = t1.pk;


pk
fk


1
1

2
null

pk	fk
1	1
2	null