Can /*+ MEMORY_QUOTA(2 GB)*/ only be placed in the outermost select? Are there any alternatives?

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

Original topic: 使用/+ MEMORY_QUOTA(2 GB)/只能放在最外层select吗？有没有什么替代方案？

| username: Jjjjayson_zeng

[TiDB Usage Environment] Production Environment
[TiDB Version]
[Reproduction Path] What operations were performed when the problem occurred
[Encountered Problem: Problem Phenomenon and Impact]
[Resource Configuration] Go to TiDB Dashboard - Cluster Info - Hosts and take a screenshot of this page
[Attachment: Screenshot/Log/Monitoring]

img_v3_0252_e62aa862-b7d6-4cf5-8e9d-8f7c5012c52g
img_v3_0252_e62aa862-b7d6-4cf5-8e9d-8f7c5012c52g1380×776 280 KB

img_v3_0252_6c4782e1-c6d9-4238-afd1-990232f949bg
img_v3_0252_6c4782e1-c6d9-4238-afd1-990232f949bg1380×776 309 KB

As shown in the picture, it works outside but not inside. Is there any solution?

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| username: Kongdom | Original post link

:thinking: Shouldn’t this be placed at the outermost layer?
You can consider modifying the system variable tidb_mem_quota_query.

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| username: 裤衩儿飞上天 | Original post link

TiDB currently supports two types of Optimizer Hints based on their scope of effect: the first type is effective within the query block scope, such as /*+ HASH_AGG() */; the second type is effective within the entire query scope, such as /*+ MEMORY_QUOTA(1024 MB)*/.

For hints effective within the query block scope, refer to: Optimizer Hints | PingCAP Documentation Center

image
image1132×873 136 KB

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| username: Kongdom | Original post link

:+1: :+1: :+1: It turns out that it also supports query block range effective Hint.

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| username: zhanggame1 | Original post link

This hint can only be placed outside.

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| username: Soysauce520 | Original post link

Specify the block with sel?

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| username: system | Original post link

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