Questions about Key TiFlash Concurrency Parameters?

This topic has been translated from a Chinese forum by GPT and might contain errors.

Original topic: 关键tiflash并发参数疑问?

| username: wenyi

May I ask, what is the difference between the parameters task_scheduler_active_set_soft_limit and tidb_max_tiflash_threads?
If tidb_max_tiflash_threads is set to 32, does that mean the concurrency for TiFlash is 32?

| username: wenyi | Original post link

The tidb_max_tiflash_threads parameter refers to a single SQL statement having a concurrency of 32?

| username: zhaokede | Original post link

The maximum is probably this much.

| username: forever | Original post link

You can refer to this, it refers to the maximum SQL concurrency per TiFlash node.

| username: yytest | Original post link


This parameter is used to set a soft limit on the active task set of the TiDB task scheduler. When the number of tasks exceeds this limit, the scheduler will attempt to reduce the execution frequency of certain tasks to avoid system overload. This parameter helps maintain system stability and prevents performance degradation caused by an excessive number of tasks.


This parameter is used to set the maximum number of threads for the TiFlash engine. TiFlash is the columnar storage engine of TiDB, responsible for handling a large number of analytical queries. By adjusting the tidb_max_tiflash_threads parameter, you can control the concurrent processing capability of the TiFlash engine, thereby optimizing query performance.

| username: 小于同学 | Original post link

Is it the largest?

| username: TiDBer_QYr0vohO | Original post link

I have encountered the same problem. It seems that the tidb_enable_clustered_index parameter is not set to ON.