lemmy/migrations/2020-12-14-020038_create_comment_aggregates/up.sql

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-- Add comment aggregates
CREATE TABLE comment_aggregates (
id serial PRIMARY KEY,
comment_id int REFERENCES COMMENT ON UPDATE CASCADE ON DELETE CASCADE NOT NULL,
score bigint NOT NULL DEFAULT 0,
upvotes bigint NOT NULL DEFAULT 0,
downvotes bigint NOT NULL DEFAULT 0,
published timestamp NOT NULL DEFAULT now(),
UNIQUE (comment_id)
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);
INSERT INTO comment_aggregates (comment_id, score, upvotes, downvotes, published)
SELECT
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c.id,
COALESCE(cl.total, 0::bigint) AS score,
COALESCE(cl.up, 0::bigint) AS upvotes,
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COALESCE(cl.down, 0::bigint) AS downvotes,
c.published
FROM
comment c
LEFT JOIN (
SELECT
l.comment_id AS id,
sum(l.score) AS total,
count(
CASE WHEN l.score = 1 THEN
1
ELSE
NULL::integer
END) AS up,
count(
CASE WHEN l.score = '-1'::integer THEN
1
ELSE
NULL::integer
END) AS down
FROM
comment_like l
GROUP BY
l.comment_id) cl ON cl.id = c.id;
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-- Add comment aggregate triggers
-- initial comment add
CREATE FUNCTION comment_aggregates_comment ()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $$
BEGIN
IF (TG_OP = 'INSERT') THEN
INSERT INTO comment_aggregates (comment_id)
VALUES (NEW.id);
ELSIF (TG_OP = 'DELETE') THEN
DELETE FROM comment_aggregates
WHERE comment_id = OLD.id;
END IF;
RETURN NULL;
END
$$;
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CREATE TRIGGER comment_aggregates_comment
AFTER INSERT OR DELETE ON comment
FOR EACH ROW
EXECUTE PROCEDURE comment_aggregates_comment ();
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-- comment score
CREATE FUNCTION comment_aggregates_score ()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $$
BEGIN
IF (TG_OP = 'INSERT') THEN
UPDATE
comment_aggregates ca
SET
score = score + NEW.score,
upvotes = CASE WHEN NEW.score = 1 THEN
upvotes + 1
ELSE
upvotes
END,
downvotes = CASE WHEN NEW.score = - 1 THEN
downvotes + 1
ELSE
downvotes
END
WHERE
ca.comment_id = NEW.comment_id;
ELSIF (TG_OP = 'DELETE') THEN
-- Join to comment because that comment may not exist anymore
UPDATE
comment_aggregates ca
SET
score = score - OLD.score,
upvotes = CASE WHEN OLD.score = 1 THEN
upvotes - 1
ELSE
upvotes
END,
downvotes = CASE WHEN OLD.score = - 1 THEN
downvotes - 1
ELSE
downvotes
END
FROM
comment c
WHERE
ca.comment_id = c.id
AND ca.comment_id = OLD.comment_id;
END IF;
RETURN NULL;
END
$$;
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CREATE TRIGGER comment_aggregates_score
AFTER INSERT OR DELETE ON comment_like
FOR EACH ROW
EXECUTE PROCEDURE comment_aggregates_score ();
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