[PERFORM] Index not used on join with inherited tables

[Sebastian Böck]

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;
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