We need documentation describing a migration path from ParquetDataset, at least for the basic user facing API of ParquetDataset (As I read it, that's: construction, projection, filtering, threading, for a first pass). Following this we could mark ParquetDataset as deprecated, building features needed by power users like dask and adding those to the migration document

Reporter: Ben Kietzman / @bkietz

Related issues:

• [Python] Long-term fate of pyarrow.parquet.ParquetDataset (is related to)
• [Python] Add user guide documentation for Datasets API (is related to)

_{Note: This issue was originally created as ARROW-8047. Please see the migration documentation for further details.}