[Feature]Support SELECT Optimizer Hints SET_VAR

[Astralidea]

Proposed changes

详细背景介绍在 Fix #4503
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代码可能写得不优雅，看看怎么去解决这个问题比较好。

[chaoyli]

A good job

[morningman]

Hi @Astralidea
Thanks for your contribution, and could you please update the document?
I think you can put it in docs/en/administrator-guide/variables.md and docs/zh-CN/administrator-guide/variables.md.
For English, you can rely on translate.google.com

[Astralidea]

Hi @Astralidea
Thanks for your contribution, and could you please update the document?
I think you can put it in docs/en/administrator-guide/variables.md and docs/zh-CN/administrator-guide/variables.md.
For English, you can rely on translate.google.com

I have updated the document, you can see if there is any need to change.

[kangkaisen]

@Astralidea Good job!. Please add a UT.

[Astralidea]

@Astralidea Good job!. Please add a UT.

好的。UT我之前看了一下，貌似不太好加，我得想想怎么加。

[kangkaisen]

@Astralidea Good job!. Please add a UT.

好的。UT我之前看了一下，貌似不太好加，我得想想怎么加。

或许可以把你的逻辑加到SelectStmt 的 analyze 方法里面，这样 SelectStmtTest 就可以直接测试，确认session 变量是否生效。

不过需要注意 context.getSessionVariable().toThrift() 要在 SelectStmt.analyze(analyzer) 之后，你可以试下。

[Astralidea]

@Astralidea Good job!. Please add a UT.

好的。UT我之前看了一下，貌似不太好加，我得想想怎么加。

或许可以把你的逻辑加到SelectStmt 的 analyze 方法里面，这样 SelectStmtTest 就可以直接测试，确认session 变量是否生效。

不过需要注意 context.getSessionVariable().toThrift() 要在 SelectStmt.analyze(analyzer) 之后，你可以试下。

我改写一下DorisAssert框架可以测了。

[kangkaisen]

+1