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Help Center/ MapReduce Service/ FAQs/ Job Development/ How Do I Do If an Alarm Is Reported Indicating that the Memory Is Insufficient When I Execute a SQL Statement on the ClickHouse Client?

How Do I Do If an Alarm Is Reported Indicating that the Memory Is Insufficient When I Execute a SQL Statement on the ClickHouse Client?

Updated on 2022-09-14 GMT+08:00

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Symptom

The ClickHouse client restricts the memory used by GROUP BY statements. When a SQL statement is executed on the ClickHouse client, the following error information is displayed:

Progress: 1.83 billion rows, 85.31 GB (68.80 million rows/s., 3.21 GB/s.)        6%Received exception from server:
Code: 241. DB::Exception: Received from localhost:9000, 127.0.0.1. 
DB::Exception: Memory limit (for query) exceeded: would use 9.31 GiB (attempt to allocate chunk of 1048576 bytes), maximum: 9.31 GiB: 
(while reading column hits):

Solution

Run the following command before executing an SQL statement on condition that the cluster has sufficient memory:
```
SET max_memory_usage = 128000000000; #128G
```

If no sufficient memory is available, ClickHouse enables you to overflow data to disk to free up the memory: You are advised to set the value of max_memory_usage to twice the size of max_bytes_before_external_group_by.
```
set max_bytes_before_external_group_by=20000000000; #20G
set max_memory_usage=40000000000; #40G
```

Parent topic: Job Development

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