Function polars_plan::logical_plan::find_column_union_and_fingerprints

pub fn find_column_union_and_fingerprints(
    root: Node,
    columns: &mut PlHashMap<FileFingerPrint, (FileCount, PlIndexSet<String>)>,
    lp_arena: &Arena<ALogicalPlan>,
    expr_arena: &Arena<AExpr>
)

Available on crate features ipc or parquet or csv or cse or json only.

Find the union between the columns per unique IO operation. A unique IO operation is the file + the predicates pushed down to that file