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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 tbl (sl_no int, username text, petname1 text, petname2 text);
INSERT INTO tbl VALUES
(1, 'A', 'XYZ', 'ABC')
, (2, 'B', 'RTS', 'DEF')
, (3, 'C', 'QWE', 'GHI')
, (4, 'D', 'HGD', 'JKL')
;
CREATE TABLE
INSERT 0 4
SELECT
t.sl_no,
t.username,
v.petname
FROM tbl t
CROSS JOIN LATERAL (VALUES
(petname1),
(petname2)
) v(petname);
| sl_no | username | petname |
|---|---|---|
| 1 | A | XYZ |
| 1 | A | ABC |
| 2 | B | RTS |
| 2 | B | DEF |
| 3 | C | QWE |
| 3 | C | GHI |
| 4 | D | HGD |
| 4 | D | JKL |
SELECT 8