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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 the_table (col3 SERIAL, col2 varchar, col1 varchar, PRIMARY KEY(col3));
INSERT INTO the_table (col2,col1) VALUES
('x','a'),
('x','b'),
('y','c'),
('y','d'),
('z','e'),
('z','f');
CREATE TABLE
INSERT 0 6
SELECT col2, MIN(col3) AS col3, MIN(col1) AS col1
FROM the_table
GROUP BY col2;
| col2 | col3 | col1 |
|---|---|---|
| z | 5 | e |
| y | 3 | c |
| x | 1 | a |
SELECT 3