@izveigor or @jayzhan211 I wonder if you have some time to review this PR?

Thanks @izveigor -- I'll keep chipping away at keeping the codebase readable and documented :)

@alamb @izveigor
I have different thoughts on this, List() is 1D, List(List()) is 2D, Int64 is 0D, dimension is only meaningful to List, not non-List type,
that is also the reason I left the comment on

PR comment:
https://github.com/apache/arrow-datafusion/pull/7008/files/b0e37747d487f89b365d19089becdf8b1b63cbe7#r1268009827

Main:
https://github.com/apache/arrow-datafusion/blob/354202922889502cf51cabf630b05003fddd2ec7/datafusion/expr/src/built_in_function.rs#L494-L497.

But, If we want a new definition of dimensions, it is also fine.

I have different thoughts on this, List() is 1D, List(List()) is 2D, Int64 is 0D, dimension is only meaningful to List, not non-List type,

But, If we want a new definition of dimensions, it is also fine.

My intention was not to change the definition but to capture what this function does. I am pretty sure that given the input int64 this function would return 1

@alamb In your opinion, which one do you prefer? I think both are fine but need to be consistent everywhere

@alamb In your opinion, which one do you prefer?

• Int64 is 0D,
• List() is 1D
• List(List()) is 2D,

Makes the most sense to me given my understanding of multi-dimensional array terminology.

I don't know the code well enough to understand how large a code change updating to that definition would be

I don't think there are many to change so changing the code might not be a problem. We just need to have a consensus on the definition of list dimensions, also add them to code comment and documentation

These are some code I know that is related to List dimensions
https://github.com/apache/arrow-datafusion/blob/11b7b5c215012231e5768fc5be3445c0254d0169/datafusion/expr/src/built_in_function.rs#L439-L460

https://github.com/apache/arrow-datafusion/blob/11b7b5c215012231e5768fc5be3445c0254d0169/datafusion/physical-expr/src/array_expressions.rs#L128-L162

https://github.com/apache/arrow-datafusion/blob/11b7b5c215012231e5768fc5be3445c0254d0169/datafusion/expr/src/built_in_function.rs#L494-L517

@izveigor Do you know any code that considers the list dimensions?