I have a table A which have ~ 200M rows and table B with same structure. Clickhouse uses in normal state up to 1k threads. I tried transfer data from A to B with query INSERT INTO B SELECT * FROM A. Thread count used by clickhouse incremented to 2k and query throws exception Code: 439. DB::Exception: Received from localhost:9000. DB::Exception: Cannot schedule a task: no free thread. After that clickhouse should decrement thread count using for query execution. But thread count still is 2k

Does it reproduce on recent release?

No , i am use clickhouse 21.12.3.32 version

How to reproduce

• Which ClickHouse server version to use
• 21.12.3.32 version
• Queries to run that lead to unexpected result
  INSERT INTO B SELECT * FROM A

Expected behavior

1k thread using by clickhouse process