Partition：按月分区和按天分区怎么选

SELECT count(DISTINCT partition) FROM system.parts WHERE table='pmonth' AND active;
→ 3    ← 真实覆盖2026年1、2、3月，正好3个分区

SELECT count(DISTINCT partition) FROM system.parts WHERE table='pday' AND active;
→ 90   ← 真实每天一个分区

SELECT value FROM system.settings WHERE name='max_partitions_per_insert_block';
→ 100

INSERT INTO demo.pday2 SELECT toDate('2020-01-01')+number, number FROM numbers(1000);
→ 真实报错：
DB::Exception: Too many partitions for single INSERT block (more than 100).
Large number of partitions is a common misconception. It will lead to
severe negative performance impact, including slow server startup,
slow INSERT queries and slow SELECT queries. Recommended total number
of partitions for a table is under 1000..10000. Please note, that
partitioning is not intended to speed up SELECT queries (ORDER BY key
is sufficient to make range queries fast). Partitions are intended for
data manipulation (DROP PARTITION, etc). (TOO_MANY_PARTS)