Window functions with summations on postgresql - sql

Question

What I'm trying to achieve is to calculate a daily, weekly and monthly leaderboard with sum(points), all-time high points and all-time low points per user (and per time-frame) but haven't had a lot of success. My schema look like:
CREATE TABLE users(
id SERIAL PRIMARY KEY,
name text NOT NULL
);
-- contains millions of rows!
CREATE TABLE results(
id SERIAL PRIMARY KEY,
user_id integer NOT NULL REFERENCES users(id),
points float NOT NULL, -- can be negative
date timestamptz NOT NULL DEFAULT NOW()
);
-- sample data
INSERT INTO users (name)
VALUES ('user1'), ('user2'), ('user3'), ('user4');
INSERT INTO results (user_id, points)
VALUES (2, -10), (1, 50), (4, -20), (3, 20), (2, 50), (4, -20), (1, 50), (1, -25), (4, 30), (3, -70), (2, 50), (1, -25), (4, 20), (2, -90), (3, 60), (4, -20);
so for example, assuming those results where correspond to the last week, the weekly leaderboard would have something like:
User|sum(points) User|ATH points User|ATL points
1 50 1 100 3 -50
3 10 2 90 4 -40
which are only calculated with the results where date is in the last week, and so on.
but in order to achieve that it seems to me that I need to somehow iterate over every bet to calculate the highest and the lowest amounts of points the user had at any point in that time-frame. Doing it in-memory isn't going to work well, because I'll need to store millions of results in memory.
Is there anyway of doing it completely in a query?. I've looked into window functions but don't see how a summation could be done using them.

Answer 1

You should use window functions to calculate the sum and the running sum (ordered by date), then take the minimum and maximum of the running sums:
SELECT user_id,
sum,
min(running) AS atl,
max(running) AS ath
FROM (SELECT user_id,
sum(points) OVER (PARTITION BY user_id),
sum(points) OVER (PARTITION BY user_id ORDER BY date) AS running
FROM results
WHERE date > current_timestamp - INTERVAL '1 week') AS q
GROUP BY user_id, sum;