Dandandan commented on code in PR #11483:
URL: https://github.com/apache/datafusion/pull/11483#discussion_r1681127065
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datafusion/core/src/physical_optimizer/pruning.rs:
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@@ -736,12 +738,22 @@ impl RequiredColumns {
Self::default()
}
- /// Returns number of unique columns
- pub(crate) fn n_columns(&self) -> usize {
- self.iter()
- .map(|(c, _s, _f)| c)
- .collect::<HashSet<_>>()
- .len()
+ /// Returns Some(column) if this is a single column predicate.
+ ///
+ /// Returns None if this is a multi-column predicate.
+ ///
+ /// Examples:
+ /// * `a > 5 OR a < 10` returns `Some(a)`
+ /// * `a > 5 OR b < 10` returns `None`
+ /// * `true` returns None
+ pub(crate) fn single_column(&self) -> Option<&phys_expr::Column> {
+ let cols = self.iter().map(|(c, _s, _f)| c).collect::<HashSet<_>>();
Review Comment:
It seems a bit wasteful to collect into a `HashSet` only to decide whether
it's a single column?
We can do e.g. `self.columns.windows(2).all(|[x, y]| x.0 == y.0)`
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