Hi all,
I'm having another problem with a query that takes to long, because
the appropriate index is not used.
I found some solutions to this problem, but I think Postgres should do
an index scan in all cases.
To show the problem I've attached a small script with a testcase.
Thanks in advance
Sebastian
/* tables */
CREATE TABLE test (
id SERIAL PRIMARY KEY,
test TEXT
);
CREATE TABLE test1 (
id INTEGER PRIMARY KEY
) INHERITS (test);
CREATE TABLE test2 (
id INTEGER PRIMARY KEY
) INHERITS (test);
CREATE TABLE test3 (
id INTEGER PRIMARY KEY
) INHERITS (test);
CREATE TABLE bug (
id INTEGER PRIMARY KEY
);
/* views */
CREATE OR REPLACE VIEW working_fast AS
SELECT *
FROM test
WHERE id = 1;
CREATE OR REPLACE VIEW working_fast_2 AS
SELECT test1.* FROM test1 JOIN bug AS bug1 ON TRUE WHERE test1.id = bug1.id
UNION ALL
SELECT test2.* FROM test2 JOIN bug AS bug2 ON TRUE WHERE test2.id = bug2.id
UNION ALL
SELECT test3.* FROM test3 JOIN bug AS bug3 ON TRUE WHERE test3.id = bug3.id;
CREATE OR REPLACE VIEW working_slow AS
SELECT test.*
FROM test
JOIN bug ON TRUE
WHERE test.id = bug.id;
/* data */
CREATE OR REPLACE FUNCTION data () RETURNS BOOLEAN AS $$
BEGIN
FOR i IN 1..10000 LOOP
INSERT INTO test1 (id,test) VALUES (DEFAULT,i);
INSERT INTO test2 (id,test) VALUES (DEFAULT,i);
INSERT INTO test3 (id,test) VALUES (DEFAULT,i);
END LOOP;
RETURN TRUE;
END;
$$ LANGUAGE plpgsql;
SELECT data();
INSERT INTO bug VALUES ('1');
ANALYZE;
EXPLAIN ANALYZE SELECT * from working_fast;
EXPLAIN ANALYZE SELECT * from working_fast_2;
EXPLAIN ANALYZE SELECT * from working_slow;
