lemmy/migrations/2020-12-10-152350_create_post_aggregates/up.sql

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-- Add post aggregates
CREATE TABLE post_aggregates (
id serial PRIMARY KEY,
post_id int REFERENCES post ON UPDATE CASCADE ON DELETE CASCADE NOT NULL,
comments bigint NOT NULL DEFAULT 0,
score bigint NOT NULL DEFAULT 0,
upvotes bigint NOT NULL DEFAULT 0,
downvotes bigint NOT NULL DEFAULT 0,
stickied boolean NOT NULL DEFAULT FALSE,
published timestamp NOT NULL DEFAULT now(),
newest_comment_time timestamp NOT NULL DEFAULT now(),
UNIQUE (post_id)
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);
INSERT INTO post_aggregates (post_id, comments, score, upvotes, downvotes, stickied, published, newest_comment_time)
SELECT
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p.id,
coalesce(ct.comments, 0::bigint) AS comments,
coalesce(pl.score, 0::bigint) AS score,
coalesce(pl.upvotes, 0::bigint) AS upvotes,
coalesce(pl.downvotes, 0::bigint) AS downvotes,
p.stickied,
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p.published,
greatest (ct.recent_comment_time, p.published) AS newest_activity_time
FROM
post p
LEFT JOIN (
SELECT
comment.post_id,
count(*) AS comments,
max(comment.published) AS recent_comment_time
FROM
comment
GROUP BY
comment.post_id) ct ON ct.post_id = p.id
LEFT JOIN (
SELECT
post_like.post_id,
sum(post_like.score) AS score,
sum(post_like.score) FILTER (WHERE post_like.score = 1) AS upvotes,
- sum(post_like.score) FILTER (WHERE post_like.score = '-1'::integer) AS downvotes
FROM
post_like
GROUP BY
post_like.post_id) pl ON pl.post_id = p.id;
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-- Add community aggregate triggers
-- initial post add
CREATE FUNCTION post_aggregates_post ()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $$
BEGIN
IF (TG_OP = 'INSERT') THEN
INSERT INTO post_aggregates (post_id)
VALUES (NEW.id);
ELSIF (TG_OP = 'DELETE') THEN
DELETE FROM post_aggregates
WHERE post_id = OLD.id;
END IF;
RETURN NULL;
END
$$;
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CREATE TRIGGER post_aggregates_post
AFTER INSERT OR DELETE ON post
FOR EACH ROW
EXECUTE PROCEDURE post_aggregates_post ();
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-- comment count
CREATE FUNCTION post_aggregates_comment_count ()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $$
BEGIN
IF (TG_OP = 'INSERT') THEN
UPDATE
post_aggregates pa
SET
comments = comments + 1
WHERE
pa.post_id = NEW.post_id;
-- A 2 day necro-bump limit
UPDATE
post_aggregates pa
SET
newest_comment_time = NEW.published
WHERE
pa.post_id = NEW.post_id
AND published > ('now'::timestamp - '2 days'::interval);
ELSIF (TG_OP = 'DELETE') THEN
-- Join to post because that post may not exist anymore
UPDATE
post_aggregates pa
SET
comments = comments - 1
FROM
post p
WHERE
pa.post_id = p.id
AND pa.post_id = OLD.post_id;
END IF;
RETURN NULL;
END
$$;
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CREATE TRIGGER post_aggregates_comment_count
AFTER INSERT OR DELETE ON comment
FOR EACH ROW
EXECUTE PROCEDURE post_aggregates_comment_count ();
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-- post score
CREATE FUNCTION post_aggregates_score ()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $$
BEGIN
IF (TG_OP = 'INSERT') THEN
UPDATE
post_aggregates pa
SET
score = score + NEW.score,
upvotes = CASE WHEN NEW.score = 1 THEN
upvotes + 1
ELSE
upvotes
END,
downvotes = CASE WHEN NEW.score = - 1 THEN
downvotes + 1
ELSE
downvotes
END
WHERE
pa.post_id = NEW.post_id;
ELSIF (TG_OP = 'DELETE') THEN
-- Join to post because that post may not exist anymore
UPDATE
post_aggregates pa
SET
score = score - OLD.score,
upvotes = CASE WHEN OLD.score = 1 THEN
upvotes - 1
ELSE
upvotes
END,
downvotes = CASE WHEN OLD.score = - 1 THEN
downvotes - 1
ELSE
downvotes
END
FROM
post p
WHERE
pa.post_id = p.id
AND pa.post_id = OLD.post_id;
END IF;
RETURN NULL;
END
$$;
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CREATE TRIGGER post_aggregates_score
AFTER INSERT OR DELETE ON post_like
FOR EACH ROW
EXECUTE PROCEDURE post_aggregates_score ();
-- post stickied
CREATE FUNCTION post_aggregates_stickied ()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $$
BEGIN
UPDATE
post_aggregates pa
SET
stickied = NEW.stickied
WHERE
pa.post_id = NEW.id;
RETURN NULL;
END
$$;
CREATE TRIGGER post_aggregates_stickied
AFTER UPDATE ON post
FOR EACH ROW
WHEN (OLD.stickied IS DISTINCT FROM NEW.stickied)
EXECUTE PROCEDURE post_aggregates_stickied ();