Add option to determine whether to convert identifiers

[jiacai2050]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

In CeresDB, we use datafusion for SQL execution, and find #1746 change unquoted identifiers to lowercase, which is a breaking change for us.

I agree with what #1746 does, but it there any possibilities to add an option to configure this? By default it will do the normalization, and users can choose not to do.

Describe the solution you'd like
Add on option to determine whether to convert identifiers.

If maintainers agree with this, I'd be glad to submit a PR.

Describe alternatives you've considered

Additional context

• Identifiers should be case-sensitive for all protocols by default horaedb#442

[jiacai2050]

@alamb Would you mind sharing your thoughts?

[alamb]

@jiacai2050 I think an option to control the case identifier behavior sounds very reasonable to me 👍

[jiacai2050]

Thanks, I will open a PR to add this.