\set ECHO none
NOTICE:  Percentiles are monotone and in range
NOTICE:  Scalar and array percentiles agree
NOTICE:  Percentiles are monotone and in range
NOTICE:  Scalar and array percentiles agree
NOTICE:  Percentiles are monotone and in range
NOTICE:  Scalar and array percentiles agree
NOTICE:  Percentiles are monotone and in range
NOTICE:  Scalar and array percentiles agree
NOTICE:  Percentiles are monotone and in range
NOTICE:  Scalar and array percentiles agree
NOTICE:  Percentiles are monotone and in range
NOTICE:  Scalar and array percentiles agree
NOTICE:  Raw and weighted percentiles are monotone
NOTICE:  Raw and weighted percentiles are monotone
NOTICE:  Inverse interpolation is monotone
NOTICE:  Scalar and array inverse percentiles agree
-- At p = 0.75 - 2^-53, q = 1 - 2^-52 and the result rounds to -5.
-- Subtracting nearly equal magnitudes used to return -4 instead.
SELECT tdigest_percentile(v, 10000, 0.7499999999999999::double precision) AS raw_scalar,
       tdigest_percentile(v, 10000, ARRAY[0.7499999999999999]::double precision[]) AS raw_array,
       tdigest_percentile(v, 1::bigint, 10000, 0.7499999999999999::double precision) AS weighted_scalar,
       tdigest_percentile(v, 1::bigint, 10000,
                          ARRAY[0.7499999999999999]::double precision[]) AS weighted_array
FROM (VALUES (-18014398509481984::double precision),
             (-1::double precision)) AS input(v);
 raw_scalar | raw_array | weighted_scalar | weighted_array 
------------+-----------+-----------------+----------------
         -5 | {-5}      |              -5 | {-5}
(1 row)

-- Also cover stored digests and count rounding that makes q exactly 1.
-- The endpoint case used to return -4, inside the bracket but not equal to -3.
WITH inputs(label, d, p) AS (
    VALUES (
        'precision',
        'flags 1 count 2 compression 10000 centroids 2 (-18014398509481984, 1) (-1, 1)'::tdigest,
        0.7499999999999999::double precision
    ), (
        'endpoint',
        'flags 1 count 9007199254743615 compression 10000 centroids 3 (-10000000000000000, 9007199254740839) (-3, 290) (-1, 2486)'::tdigest,
        0.9999999999997077::double precision
    )
)
SELECT label, tdigest_percentile(d, p) AS scalar_result,
       tdigest_percentile(d, ARRAY[p]) AS array_result
FROM inputs
GROUP BY label
ORDER BY label;
   label   | scalar_result | array_result 
-----------+---------------+--------------
 endpoint  |            -3 | {-3}
 precision |            -5 | {-5}
(2 rows)