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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 questions (
question_id serial PRIMARY KEY
, title text NOT NULL
, body text
, userid int
, categoryid int
);
CREATE TABLE tags (
tag_id serial PRIMARY KEY
, tag text NOT NULL UNIQUE
);
CREATE TABLE questiontags (
question_id int REFERENCES questions
, tag_id int REFERENCES tags
, PRIMARY KEY(question_id, tag_id)
);
WITH input_data(body, userid, title, categoryid, tags) AS (
VALUES ('some_body2', 3, 'some_title2', 5, '{foo1, bar, baz}')
)
, input_tags AS (
SELECT DISTINCT tag -- fold duplicates
FROM input_data, unnest(tags::text[]) tag
)
, q AS ( -- insert into questions
INSERT INTO questions
(body, userid, title, categoryid)
SELECT body, userid, title, categoryid
FROM input_data
RETURNING question_id
)
, t AS ( -- insert into tags
INSERT INTO tags (tag)
TABLE input_tags -- short for: SELECT * FROM input_tags
ON CONFLICT (tag) DO NOTHING -- only new tags
RETURNING tag_id
)
INSERT INTO questiontags (question_id, tag_id)
SELECT q.question_id, t.tag_id
FROM q, (
SELECT tag_id FROM t
UNION ALL
SELECT tag_id FROM input_tags JOIN tags USING (tag)
) t;
3 rows affected
TABLE questions;
| question_id | title | body | userid | categoryid |
|---|---|---|---|---|
| 1 | some_title2 | some_body2 | 3 | 5 |
TABLE tags;
| tag_id | tag |
|---|---|
| 1 | bar |
| 2 | foo1 |
| 3 | baz |
TABLE questiontags;
| question_id | tag_id |
|---|---|
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |