lemmy/migrations/2020-12-04-183345_create_community_aggregates/up.sql

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-- Add community aggregates
CREATE TABLE community_aggregates (
id serial PRIMARY KEY,
community_id int REFERENCES community ON UPDATE CASCADE ON DELETE CASCADE NOT NULL,
subscribers bigint NOT NULL DEFAULT 0,
posts bigint NOT NULL DEFAULT 0,
comments bigint NOT NULL DEFAULT 0,
published timestamp NOT NULL DEFAULT now(),
UNIQUE (community_id)
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);
INSERT INTO community_aggregates (community_id, subscribers, posts, comments, published)
SELECT
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c.id,
coalesce(cf.subs, 0) AS subscribers,
coalesce(cd.posts, 0) AS posts,
coalesce(cd.comments, 0) AS comments,
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c.published
FROM
community c
LEFT JOIN (
SELECT
p.community_id,
count(DISTINCT p.id) AS posts,
count(DISTINCT ct.id) AS comments
FROM
post p
LEFT JOIN comment ct ON p.id = ct.post_id
GROUP BY
p.community_id) cd ON cd.community_id = c.id
LEFT JOIN (
SELECT
community_follower.community_id,
count(*) AS subs
FROM
community_follower
GROUP BY
community_follower.community_id) cf ON cf.community_id = c.id;
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-- Add community aggregate triggers
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-- initial community add
CREATE FUNCTION community_aggregates_community ()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $$
BEGIN
IF (TG_OP = 'INSERT') THEN
INSERT INTO community_aggregates (community_id)
VALUES (NEW.id);
ELSIF (TG_OP = 'DELETE') THEN
DELETE FROM community_aggregates
WHERE community_id = OLD.id;
END IF;
RETURN NULL;
END
$$;
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CREATE TRIGGER community_aggregates_community
AFTER INSERT OR DELETE ON community
FOR EACH ROW
EXECUTE PROCEDURE community_aggregates_community ();
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-- post count
CREATE FUNCTION community_aggregates_post_count ()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $$
BEGIN
IF (TG_OP = 'INSERT') THEN
UPDATE
community_aggregates
SET
posts = posts + 1
WHERE
community_id = NEW.community_id;
ELSIF (TG_OP = 'DELETE') THEN
UPDATE
community_aggregates
SET
posts = posts - 1
WHERE
community_id = OLD.community_id;
-- Update the counts if the post got deleted
UPDATE
community_aggregates ca
SET
posts = coalesce(cd.posts, 0),
comments = coalesce(cd.comments, 0)
FROM (
SELECT
c.id,
count(DISTINCT p.id) AS posts,
count(DISTINCT ct.id) AS comments
FROM
community c
LEFT JOIN post p ON c.id = p.community_id
LEFT JOIN comment ct ON p.id = ct.post_id
GROUP BY
c.id) cd
WHERE
ca.community_id = OLD.community_id;
END IF;
RETURN NULL;
END
$$;
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CREATE TRIGGER community_aggregates_post_count
AFTER INSERT OR DELETE ON post
FOR EACH ROW
EXECUTE PROCEDURE community_aggregates_post_count ();
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-- comment count
CREATE FUNCTION community_aggregates_comment_count ()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $$
BEGIN
IF (TG_OP = 'INSERT') THEN
UPDATE
community_aggregates ca
SET
comments = comments + 1
FROM
comment c,
post p
WHERE
p.id = c.post_id
AND p.id = NEW.post_id
AND ca.community_id = p.community_id;
ELSIF (TG_OP = 'DELETE') THEN
UPDATE
community_aggregates ca
SET
comments = comments - 1
FROM
comment c,
post p
WHERE
p.id = c.post_id
AND p.id = OLD.post_id
AND ca.community_id = p.community_id;
END IF;
RETURN NULL;
END
$$;
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CREATE TRIGGER community_aggregates_comment_count
AFTER INSERT OR DELETE ON comment
FOR EACH ROW
EXECUTE PROCEDURE community_aggregates_comment_count ();
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-- subscriber count
CREATE FUNCTION community_aggregates_subscriber_count ()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $$
BEGIN
IF (TG_OP = 'INSERT') THEN
UPDATE
community_aggregates
SET
subscribers = subscribers + 1
WHERE
community_id = NEW.community_id;
ELSIF (TG_OP = 'DELETE') THEN
UPDATE
community_aggregates
SET
subscribers = subscribers - 1
WHERE
community_id = OLD.community_id;
END IF;
RETURN NULL;
END
$$;
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CREATE TRIGGER community_aggregates_subscriber_count
AFTER INSERT OR DELETE ON community_follower
FOR EACH ROW
EXECUTE PROCEDURE community_aggregates_subscriber_count ();
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