Postgres 14

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 words_users (
    uid SERIAL PRIMARY KEY,
    muted BOOLEAN NOT NULL DEFAULT false
);

CREATE TABLE words_social (
    sid     text     NOT NULL CHECK (sid ~ '\S'),
    social  integer  NOT NULL CHECK (0 < social AND social <= 256),
    given   text     NOT NULL CHECK (given ~ '\S'),
    uid     integer  NOT NULL REFERENCES words_users ON DELETE CASCADE,
    PRIMARY KEY(sid, social)
);

CREATE TABLE words_games (
    gid      SERIAL PRIMARY KEY,
    player1  integer REFERENCES words_users(uid) ON DELETE CASCADE NOT NULL CHECK (player1 <> player2),
    player2  integer REFERENCES words_users(uid) ON DELETE CASCADE
);

CREATE TABLE words_chat (
        cid     BIGSERIAL PRIMARY KEY,
        created timestamptz NOT NULL,
        gid     integer NOT NULL REFERENCES words_games ON DELETE CASCADE,
        uid     integer NOT NULL REFERENCES words_users ON DELETE CASCADE,
        msg     text    NOT NULL
);

-- create 2 users: one is ok, while the other is muted (punished)
INSERT INTO words_users (uid, muted) VALUES 
(1, false), 
(2, true), 
(3, false);

INSERT INTO words_social (sid, social, given, uid) VALUES 
('abc', 100, 'Nice user #1', 1), 
('def', 200, 'Bad user', 2), 
('ghi', 100, 'Nice user #2', 3);

-- put these 2 users into a game number 10
INSERT INTO words_games (gid, player1, player2) VALUES 
(10, 1, 2),
(20, 1, 3);

-- start chatting
INSERT INTO words_chat (gid, uid, created, msg) VALUES
(10, 1, CURRENT_TIMESTAMP + INTERVAL '1 min', 'Hi how are you doing?'),
(10, 1, CURRENT_TIMESTAMP + INTERVAL '2 min', 'I am a nice user #1'),
(10, 2, CURRENT_TIMESTAMP + INTERVAL '3 min', 'F*** ***!!'),
(10, 2, CURRENT_TIMESTAMP + INTERVAL '4 min', 'I am a bad user'),
(10, 1, CURRENT_TIMESTAMP + INTERVAL '5 min', 'Are you there??'),
(20, 1, CURRENT_TIMESTAMP + INTERVAL '1 min', 'Another game, hello'),
(20, 3, CURRENT_TIMESTAMP + INTERVAL '2 min', 'I am a nice user #2');

CREATE OR REPLACE FUNCTION words_get_uid(
                in_social integer,
                in_sid    text
        ) RETURNS integer AS
$func$
        SELECT uid 
        FROM words_social
        WHERE social = in_social
        AND sid = in_sid;
$func$ LANGUAGE sql IMMUTABLE;

CREATE OR REPLACE FUNCTION words_get_chat(
                in_gid   integer,
                in_uid   integer
        ) RETURNS TABLE (
                out_mine integer,
                out_game text,
                out_msg  text
        ) AS
$func$
        SELECT
                CASE WHEN c.uid = in_uid THEN 1 ELSE 0 END,
                'game #' || c.gid,
                c.msg
        FROM    words_chat c
        JOIN    words_games g USING (gid) 
        JOIN    words_users opponent ON (opponent.uid IN (g.player1, g.player2) AND opponent.uid <> in_uid)
        WHERE   c.gid = in_gid
        -- always show myself my own chat messages
        AND     c.uid = in_uid 
        -- otherwise only show messages by not muted opponents
        OR      NOT opponent.muted
        ORDER BY c.created ASC;

$func$ LANGUAGE sql;

SELECT words_get_chat(10, words_get_uid(100, 'abc')) AS nice_user;

SELECT words_get_chat(10, words_get_uid(200, 'def')) AS muted_user;

3 rows affected

3 rows affected

2 rows affected

7 rows affected

nice_user
(1,"game #10","Hi how are you doing?")
(1,"game #20","Another game, hello")
(1,"game #10","I am a nice user #1")
(0,"game #20","I am a nice user #2")
(1,"game #10","Are you there??")

muted_user
(0,"game #20","Another game, hello")
(0,"game #20","Another game, hello")
(0,"game #10","Hi how are you doing?")
(0,"game #20","I am a nice user #2")
(0,"game #10","I am a nice user #1")
(0,"game #20","I am a nice user #2")
(1,"game #10","F* *!!")
(1,"game #10","I am a bad user")
(0,"game #10","Are you there??")