CREATE MATERIALIZED VIEW foo.events_importance (
    `count` AggregateFunction(count),
    `time` DateTime('UCT'),
    `importance` String,
    `_date` Date
) ENGINE = AggregatingMergeTree()
PARTITION BY toDate(time)
ORDER BY (toDate(time), importance)
SETTINGS index_granularity = 8192 AS
SELECT
    countState() AS count,
    toStartOfMinute(toDateTime(time)) AS time,
    importance,
    toDate(time) AS _date
FROM foo.events
GROUP BY time, importance

20.13.1.5273
create table trg(A Int64, S String) Engine=MergeTree order by A;
cl -q ' select toInt64(number) A, toString(number) S from numbers(100000000) format TSV' > t.tsv
cl --max_insert_block_size=100000000  -q 'insert into trg format TSV' <t.tsv
select count(), min(rows), max(rows) from system.parts where active and table='trg'
┌─count()─┬─min(rows)─┬─max(rows)─┐
│       1 │ 100000000 │ 100000000 │
└─────────┴───────────┴───────────┘

truncate table trg;
cl -q ' select toInt64(number) A, toString(number) S from numbers(100000000) format Native' > t.native
cl --max_insert_block_size=100000000  -q 'insert into trg format Native' <t.native
select count(), min(rows), max(rows) from system.parts where active and table='trg'
┌─count()─┬─min(rows)─┬─max(rows)─┐
│       6 │    890935 │  32293965 │
└─────────┴───────────┴───────────┘