adriangb commented on code in PR #19129:
URL: https://github.com/apache/datafusion/pull/19129#discussion_r2600270186
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datafusion/pruning/src/pruning_predicate.rs:
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@@ -1545,6 +1588,50 @@ fn build_predicate_expression(
.unwrap_or_else(|_| unhandled_hook.handle(expr))
}
+/// Count of distinct column references in an expression.
+/// This is the same as [`collect_columns`] but optimized to stop counting
+/// once more than one distinct column is found.
+///
+/// For example, in expression `col1 + col2`, the count is `Many`.
+/// In expression `col1 + 5`, the count is `One`.
+/// In expression `5 + 10`, the count is `Zero`.
+///
+/// [`collect_columns`]: datafusion_physical_expr::utils::collect_columns
+#[derive(Debug, PartialEq, Eq)]
+enum ColumnReferenceCount {
+ /// no column references
+ Zero,
+ /// Only one column reference
+ One(phys_expr::Column),
+ /// More than one column reference
+ Many,
+}
+
+impl ColumnReferenceCount {
+ /// Count the number of distinct column references in an expression
+ fn from_expression(expr: &Arc<dyn PhysicalExpr>) -> Self {
+ let mut seen = HashSet::<phys_expr::Column>::new();
+ expr.apply(|expr| {
+ if let Some(column) =
expr.as_any().downcast_ref::<phys_expr::Column>() {
+ seen.insert(column.clone());
+ if seen.len() > 1 {
Review Comment:
I think because `len() > 1` != `len >= 1`
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