Help Center/ MapReduce Service/ Component Operation Guide (Normal)/ Using ClickHouse/ ClickHouse Performance Tuning/ Accelerating TTL Operations
Updated on 2025-10-23 GMT+08:00
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Accelerating TTL Operations

When TTL is triggered in ClickHouse, a large amount of CPU and memory are consumed.

Log in to FusionInsight Manager and choose Cluster > Services > ClickHouse. Click Configurations then All Configurations. Click ClickHouseServer > Customization, find the clickhouse-config-customize parameter, add the following parameters, save the configuration, and restart the service.

Configuration Item

Reference Value

Description

merge_tree.max_replicated_merges_with_ttl_in_queue

Half of number of CPU cores

Number of tasks that allow TTL to merge parts concurrently in the ReplicatedMergeTree queue.

merge_tree.max_number_of_merges_with_ttl_in_pool

Number of CPU cores

The thread pool that allows TTL to merge parts in the ReplicatedMergeTree queue.
  • Do not modify these configurations when the cluster writes heavily. Idle threads need to be reserved for regular Merge operations to avoid the "Too many parts" issue.
  • For large tables with over 100 million records, use a scheduled task to implement data aging instead of modifying or setting TTL. To do this, run alter table table_name on cluster default_cluster drop partition partition_name.