PRAGMA config.flags('OptimizerFlags', 'PushdownFiltersOverWindow');
USE plato;

$windowed = (
    SELECT key, value,
        MAX(value) OVER (PARTITION BY key) AS max_value
    FROM Input
);

INSERT INTO Output
SELECT key,
    SESSION_START() OVER w AS sess
FROM $windowed
WINDOW w AS (PARTITION BY key, SessionWindow(CAST(key AS Datetime), Interval('P1D')));