DROP TABLE IF EXISTS test;
CREATE TABLE test(date Date, keys Array(Nullable(UInt8))) ENGINE = MergeTree(date, date, 1);
INSERT INTO test VALUES ('2017-09-10', [1, 2, 3, 4, 5, 6, 7, NULL]);
SELECT * FROM test LIMIT 1;
SELECT avgArray(keys) FROM test;
DROP TABLE test;