SELECT count() 
FROM test  
WHERE (event_type_model_loaded = 1) AND (event_owner = '123') AND (event_date >= '2019-01-01') AND (event_date < '2019-10-01') 
 
┌─count()─┐ 
│ 6811866 │ 
└─────────┘ 
 
1 rows in set. Elapsed: 0.426 sec. Processed 21.40 million rows, 343.35 MB (50.22 million rows/s., 805.88 MB/s.)  
 
SELECT count() 
FROM test 
SAMPLE 5 / 10  
WHERE (event_type_model_loaded = 1) AND (event_owner = '123') AND (event_date >= '2019-01-01') AND (event_date < '2019-10-01') 
 
┌─count()─┐ 
│ 3406765 │ 
└─────────┘ 
 
1 rows in set. Elapsed: 1.375 sec. Processed 21.37 million rows, 684.94 MB (15.54 million rows/s., 498.12 MB/s.)

ORDER BY (event_owner, event_object_id, event_date, cityHash64(toString(client_id)))
SAMPLE BY cityHash64(toString(client_id))