lemmy/migrations/2020-12-14-020038_create_co.../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,
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published timestamp not null default now(),
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unique (comment_id)
);
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insert into comment_aggregates (comment_id, score, upvotes, downvotes, published)
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select
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
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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;
-- Add comment aggregate triggers
-- initial comment add
create function comment_aggregates_comment()
returns trigger language plpgsql
as $$
begin
IF (TG_OP = 'INSERT') THEN
insert into comment_aggregates (comment_id) values (NEW.id);
ELSIF (TG_OP = 'DELETE') THEN
delete from comment_aggregates where comment_id = OLD.id;
END IF;
return null;
end $$;
create trigger comment_aggregates_comment
after insert or delete on comment
for each row
execute procedure comment_aggregates_comment();
-- comment score
create function comment_aggregates_score()
returns trigger language plpgsql
as $$
begin
IF (TG_OP = 'INSERT') THEN
update comment_aggregates ca
set score = score + NEW.score,
upvotes = case when NEW.score = 1 then upvotes + 1 else upvotes end,
downvotes = case when NEW.score = -1 then downvotes + 1 else downvotes end
where ca.comment_id = NEW.comment_id;
ELSIF (TG_OP = 'DELETE') THEN
-- Join to comment because that comment may not exist anymore
update comment_aggregates ca
set score = score - OLD.score,
upvotes = case when OLD.score = 1 then upvotes - 1 else upvotes end,
downvotes = case when OLD.score = -1 then downvotes - 1 else downvotes end
from comment c
where ca.comment_id = c.id
and ca.comment_id = OLD.comment_id;
END IF;
return null;
end $$;
create trigger comment_aggregates_score
after insert or delete on comment_like
for each row
execute procedure comment_aggregates_score();