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

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2020-12-04 21:35:46 +00:00
-- 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,
posts bigint not null,
comments bigint not null,
unique (community_id)
);
insert into community_aggregates (community_id, subscribers, posts, comments)
select
c.id,
coalesce(cf.subs, 0::bigint) as subscribers,
coalesce(cd.posts, 0::bigint) as posts,
coalesce(cd.comments, 0::bigint) as comments
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;
-- Add community aggregate triggers
-- post count
create function community_aggregates_post_count()
returns trigger language plpgsql
as $$
begin
IF (TG_OP = 'INSERT') THEN
update community_aggregates
set posts = posts + 1 where community_id = NEW.community_id;
ELSIF (TG_OP = 'DELETE') THEN
update community_aggregates
set posts = posts - 1 where community_id = OLD.community_id;
END IF;
return null;
end $$;
create trigger community_aggregates_post_count
after insert or delete on post
execute procedure community_aggregates_post_count();
-- comment count
create function community_aggregates_comment_count()
returns trigger language plpgsql
as $$
begin
IF (TG_OP = 'INSERT') THEN
update community_aggregates
set comments = comments + 1 from comment c join post p on p.id = c.post_id and p.id = NEW.post_id;
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ELSIF (TG_OP = 'DELETE') THEN
update community_aggregates
set comments = comments - 1 from comment c join post p on p.id = c.post_id and p.id = OLD.post_id;
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END IF;
return null;
end $$;
create trigger community_aggregates_comment_count
after insert or delete on comment
execute procedure community_aggregates_comment_count();
-- subscriber count
create function community_aggregates_subscriber_count()
returns trigger language plpgsql
as $$
begin
IF (TG_OP = 'INSERT') THEN
update community_aggregates
set subscribers = subscribers + 1 where community_id = NEW.community_id;
ELSIF (TG_OP = 'DELETE') THEN
update community_aggregates
set subscribers = subscribers - 1 where community_id = OLD.community_id;
END IF;
return null;
end $$;
create trigger community_aggregates_subscriber_count
after insert or delete on community_follower
execute procedure community_aggregates_subscriber_count();