By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
Help with an interesting Postgres question: Why isn't an Index Only Scan used on a partition accessed via the parent table?.
CREATE TABLE a (
a_id int NOT NULL,
a_prop text NOT NULL
);
CREATE TABLE b (
b_id int NOT NULL,
b_prop text NOT NULL
);
INSERT INTO a VALUES (1, 'blah'), (2, 'blah'), (4, 'not this one');
INSERT INTO b VALUES (1, 'blah'), (3, 'blah'), (5, 'not this one');
3 rows affected
3 rows affected
SELECT *
FROM a
FULL OUTER JOIN b ON a_id = b_id
WHERE (a_prop = 'blah' OR a_prop IS NULL)
AND (b_prop = 'blah' OR b_prop IS NULL);
| a_id | a_prop | b_id | b_prop |
|---|---|---|---|
| 1 | blah | 1 | blah |
| 2 | blah | null | null |
| null | null | 3 | blah |
SELECT *
FROM a
LEFT JOIN b ON a_id = b_id
WHERE a_prop = 'blah'
AND (b_prop = 'blah' OR b_prop IS NULL);
| a_id | a_prop | b_id | b_prop |
|---|---|---|---|
| 1 | blah | 1 | blah |
| 2 | blah | null | null |
SELECT *
FROM a
LEFT JOIN b ON a_id = b_id AND b_prop = 'blah'
WHERE a_prop = 'blah';
| a_id | a_prop | b_id | b_prop |
|---|---|---|---|
| 1 | blah | 1 | blah |
| 2 | blah | null | null |