-- Finalizing a prefix window must not change the state used for later
-- frames. Compare all three builders with independent aggregation of the
-- same ordered input. This is an equality check between two executions of
-- tdigest, not a claim that its estimates equal exact percentiles.
--
-- Before the fix, each builder disagrees on 62 of the 100 frames.
-- After the fix, this script succeeds and leaves no database objects behind.

SET max_parallel_workers_per_gather = 0;

DO $$
DECLARE
    raw_mismatches bigint;
    weighted_mismatches bigint;
    merged_mismatches bigint;
BEGIN
    WITH inputs AS (
        SELECT i, tdigest_add(NULL::tdigest, i::double precision, 100) AS d
          FROM generate_series(1, 100) AS t(i)
    ), windows AS (
        SELECT i,
               tdigest(i::double precision, 100) OVER w AS raw,
               tdigest(i::double precision, 1::bigint, 100) OVER w AS weighted,
               tdigest(d) OVER w AS merged
          FROM inputs
        WINDOW w AS (ORDER BY i ROWS UNBOUNDED PRECEDING)
    ), compared AS (
        SELECT w.*,
               (SELECT tdigest(j::double precision, 100 ORDER BY j)
                  FROM generate_series(1, w.i) AS t(j)) AS expected
          FROM windows w
    )
    SELECT count(*) FILTER (WHERE tdigest_send(raw)
                                  IS DISTINCT FROM tdigest_send(expected)),
           count(*) FILTER (WHERE tdigest_send(weighted)
                                  IS DISTINCT FROM tdigest_send(expected)),
           count(*) FILTER (WHERE tdigest_send(merged)
                                  IS DISTINCT FROM tdigest_send(expected))
      INTO raw_mismatches, weighted_mismatches, merged_mismatches
      FROM compared;

    IF raw_mismatches <> 0 OR weighted_mismatches <> 0 OR merged_mismatches <> 0 THEN
        RAISE EXCEPTION 'window finalization changed reusable state: raw %, weighted %, merged % mismatches',
                        raw_mismatches, weighted_mismatches, merged_mismatches;
    END IF;
END
$$;