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-- Prior to this, the count endpoint was super naive and just ran COUNT(1).
-- This is slow asf. Now that we have an amount of actual traffic,
-- stop doing that!
-- This basically maintains a count, so we can read ONE row, instead of ALL the
-- rows. Much better.
-- Future optimisation could use some sort of cache so we don't even need to hit
-- postgres at all.
create table total_history_count_user(
id bigserial primary key,
user_id bigserial,
total integer -- try and avoid using keywords - hence total, not count
);
create or replace function user_history_count()
returns trigger as
$func$
begin
if (TG_OP='INSERT') then
update total_history_count_user set total = total + 1 where user_id = new.user_id;
if not found then
insert into total_history_count_user(user_id, total)
values (
new.user_id,
(select count(1) from history where user_id = new.user_id)
);
end if;
elsif (TG_OP='DELETE') then
update total_history_count_user set total = total - 1 where user_id = new.user_id;
if not found then
insert into total_history_count_user(user_id, total)
values (
new.user_id,
(select count(1) from history where user_id = new.user_id)
);
end if;
end if;
return NEW; -- this is actually ignored for an after trigger, but oh well
end;
$func$
language plpgsql volatile -- pldfplplpflh
cost 100; -- default value
create trigger tg_user_history_count
after insert or delete on history
for each row
execute procedure user_history_count();
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