rapimo

CREATE EXTENSION istore;
CREATE TABLE data AS
SELECT (i%30)::int as event_id, (random()*100 + 10)::int as events
FROM generate_series(1,1e6) i;

SELECT
SUM(events) FILTER (WHERE event_id = 0) as "0_events",
SUM(events) FILTER (WHERE event_id = 1) as "1_events",
SUM(events) FILTER (WHERE event_id = 2) as "2_events",
SUM(events) FILTER (WHERE event_id = 3) as "3_events",

rapimo

-- sample data
set max_parallel_workers_per_gather=1;

CREATE TABLE data AS
SELECT n, chr(n) as g, i FROM generate_series(97,122) n, generate_series(1,1e6) i ORDER BY i;

SELECT CASE g
    WHEN 'a' THEN 'one'
    WHEN 'b' THEN 'one'
    WHEN 'c' THEN 'one'