after change storage policy from cold_disk to s3, weird merge

[zdyj3170101136]

version

22.9.2

queation

out old storage policy is hot_to_cold, it store data into disk.
new storage policy is hot_to_cold_s3 it store data into s3.

after change storage policy, there are a lot of weird system.merges:
it read data from cold disk, and then write back to it.

after kill this mutation, the weird merge is closed.

create table sql

old :

CREATE TABLE default.jaeger_spans_local
(
    `timestamp` DateTime('UTC') CODEC(Delta(4), ZSTD(1)),
)
ENGINE = MergeTree
PARTITION BY toDate(timestamp)
ORDER BY (-toUnixTimestamp(timestamp))
TTL timestamp + toIntervalDay(7), timestamp + toIntervalDay(1) TO DISK 'cold_disk'
SETTINGS index_granularity = 1024, storage_policy = 'hot_to_cold'

new:

CREATE TABLE default.jaeger_spans_local
(
    `timestamp` DateTime('UTC') CODEC(Delta(4), ZSTD(1)),
)
ENGINE = MergeTree
PARTITION BY toDate(timestamp)
ORDER BY (-toUnixTimestamp(timestamp))
TTL timestamp + toIntervalDay(7), timestamp + toIntervalDay(1) TO DISK 'cold_disk_s3'
SETTINGS index_granularity = 1024, storage_policy = 'hot_to_cold_s3'

[DerekChia]

@zdyj3170101136 can you explain further what you mean by weird merges? Are you referring to the source_part_names: ['20221013_12043_15272_5'] and result_part_name: 20221013_12043_15272_5_126320?