CREATE TABLE purchase (
ts TIMESTAMP NOT NULL LATENESS INTERVAL 1 HOUR,
amount BIGINT
) WITH ('append_only' = 'true'); 

CREATE MATERIALIZED VIEW join_lateness_view
WITH ('emit_final' = 'a_ts')
AS
SELECT
  a.ts AS a_ts,
  a.amount + b.amount AS total
FROM purchase a
JOIN purchase b
ON a.ts = b.ts;