Avoid create tables with system column names

[wuchong]

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• I searched in the issues and found nothing similar.

Motivation

#640 introduced some system columns (__offset, __timestamp, __bucket) for lake enabled tables. We should throw exceptions during the creation of the table (even if lake is not enabled for them). This allows users to enable lake for the tables in the future without throwing exceptions.

Solution

No response

Anything else?

No response

Willingness to contribute

• I'm willing to submit a PR!

[zhaomin1423]

Could you assign it to me?

[MehulBatra]

@wuchong After reviewing the requirements, I propose an implementation. Please let me know if this sounds correct to you. If so I can help @zhaomin1423 to get this started.

1. Create a static unmodifiableList containing the system column names (__offset, __timestamp, __bucket) that are reserved for lake-enabled tables

2. Enhance the validation in src/main/java/com/alibaba/fluss/server/utils/TableDescriptorValidation.java to:

   • Always validate against reserved system column names during table creation, regardless of whether lake is currently enabled

3. In the validateTableDescriptor method:

   • Check if the table DDL request contains any of the reserved system column names
   • If found, throw an exception with a clear message explaining that these are reserved for internal system use

4. Add a Unit Test for the same.

5. Consider adding documentation that explains the reserved column name restrictions and their purpose(can be done as a separate part, as we might need to consider a separate page, which will contain all the system reserved keywords)

[wuchong]

@MehulBatra the proposal sounds great to me!

@zhaomin1423 are you interested in implementing this?

[zhaomin1423]

@MehulBatra the proposal sounds great to me!

@zhaomin1423 are you interested in implementing this?

Yes, thanks @MehulBatra