gistfile1.txt

Pairs of sets on dates = [[128, "2017-01-01"],[128, "2017-02-01"],[128, "2017-03-01"],[128, "2017-04-01"],[128, "2017-05-01"],
[256, "2017-06-01"],[256, "2017-07-01"],[256, "2017-08-01"],[256, "2017-09-01"],[256, "2017-10-01"]]

| id | set_id |        date |
|  1 |    128 | "2017-01-01"|
|  2 |    128 | "2017-02-01"|
|  3 |    128 | "2017-03-01"|
|  4 |    128 | "2017-04-01"|
|  5 |    128 | "2017-05-01"|
|  6 |    128 | "2017-06-01"|
|  7 |    128 | "2017-07-01"|
|  8 |    128 | "2017-08-01"|
|  9 |    128 | "2017-09-01"|
| 10 |    128 | "2017-10-01"|
| 11 |    256 | "2017-01-01"|
| 12 |    256 | "2017-02-01"|
| 13 |    256 | "2017-03-01"|
| 14 |    256 | "2017-04-01"|
| 15 |    256 | "2017-05-01"|
| 16 |    256 | "2017-06-01"|
| 17 |    256 | "2017-07-01"|
| 18 |    256 | "2017-08-01"|

We want to select the ids from the table for the array of pairs above AND in
a separate query, select which pairs are missing from the table.

SELECT set_dates.id FROM set_dates WHERE ROW(set_id, date) IN (
(128, '2017-01-01'),
(128, '2017-02-01'),
(128, '2017-03-01'),
(128, '2017-04-01'),
(128, '2017-05-01'),
(256, '2017-06-01'),
(256, '2017-07-01'),
(256, '2017-08-01'),
(256, '2017-09-01'),
(256, '2017-10-01'))


SELECT * FROM set_dates 
    RIGHT OUTER JOIN (
        SELECT * FROM UNNEST(
            ARRAY[128,128,128,128,128,256,256,256,256,256]::integer[],
            ARRAY['2017-01-01', '2017-02-01', '2017-03-01', '2017-04-01', '2017-05-01', '2017-06-01', '2017-07-01', '2017-08-01', '2017-09-01', '2017-10-01']::date[]
            ) AS t(set_id, date) 
        ) AS ary
    ON set_dates.date = ary.date AND set_dates.set_id = ary.set_id
    WHERE id IS NULL;

http://sqlfiddle.com/#!15/3a4cb/1