fix: check leaf column is root column in Parquet schema

[burmecia]

Which issue does this PR close?

N/A

What changes are included in this PR?

This PR is to fix a bug in checking if a leaf column is root column in Parquet schema. The current solution is to compare the leaf column's index with root column's index, this is not reliable as the column index may not correspond exactly after a nested column. For example,

• col A: String
• col B: Map
  • key B.K: String
  • value B.V: String
• col C: String

For column A, B.K and B.V, the currently logic works well. It won't return error for A, but will do for B.K and B.V, this is correct. But for column C, it will return error as its leaf column index (3) will not match root column index (2), this is incorrect. Column C is a valid leaf column to be in a predicate.

I think get_column_root().is_group() may be a more reliable way to check in this situation. Just to check if a leaf column's root column is a group column, we can determine a leaf column is actually on the root.

Are these changes tested?

Yes

[Xuanwo]

Nice fix, thank you!