[ARROW-18288] [GO]: pqarrow (github.com/apache/arrow/go/v9/parquet/pqarrow) cannot handle arrow's DICTIONARY field

• Type: Bug
• Status: In Progress
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 9.0.0, 10.0.0
• Component/s: Go, Parquet
• External issue URL: https://github.com/apache/arrow/issues/33466
• Assignee: Matthew Topol
• Reporter: Kevin Yang
• Created: 09/Nov/22 00:13
• Updated: 11/Jan/23 11:59

Description

Hey, Arrow Go Dev:
 
I was trying to save some arrow tables out to parquet files, with the help of the "github.com/apache/arrow/go/v9/parquet/pqarrow" package. btw, it's generally a great design (of Arrow) and a great Go implementation. 

 
However, one issue sticks out: in my original arrow Table I have some DICTIONARY fields, which pqarrow does NOT currently support.
 
I would assume supporting them will be quite straightward: just "denormalize" the DICTIONARY value into corresponding values (string, Timestamp, etc), and it's up to the Parquet to do the right trick (using DICTIONARY encoding, etc). 
 
I would have done this conversion on-the-fly by myself, by converting each DICTIONARY field into underlying values. However, the arrow table schema is dynamic and outside my control, and I need to iterate through fields (maybe structs) to locate those) -> it would be much better if pqarrow can support this natively. 
 
Can anyone help? thanks!