In HdfsScanNode.init() we try to assign dictionary and collection conjuncts even for non-Parquet scans. Such predicates only make sense for Parquet scans, so there is no point in collecting them for other scans.
The current behavior is undesirable because:
- init() can be substantially slower because assigning dictionary filters may involve evaluating exprs in the BE which can be expensive
- the explain plan of non-Parquet scans may have a section "parquet dictionary predicates" which is confusing/misleading
Relevant code snippet from HdfsScanNode: