chore: Clarify EmptyRelation description (#17157)

comphead · web-flow · commit e5b76f7ec634 · 2025-08-12T13:30:46.000-07:00
* chore: Clarify `EmptyRelation` description
diff --git a/datafusion/expr/src/logical_plan/plan.rs b/datafusion/expr/src/logical_plan/plan.rs
@@ -2040,7 +2040,9 @@ impl ToStringifiedPlan for LogicalPlan {
     }
 }
 
-/// Produces no rows: An empty relation with an empty schema
+/// Relationship produces 0 or 1 placeholder rows with specified output schema
+/// In most cases the output schema for `EmptyRelation` would be empty,
+/// however, it can be non-empty typically for optimizer rules
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct EmptyRelation {
     /// Whether to produce a placeholder row

Original file line number	Diff line number	Diff line change
`@@ -2040,7 +2040,9 @@ impl ToStringifiedPlan for LogicalPlan {`
`2040`	`2040`	`}`
`2041`	`2041`	`}`
`2042`	`2042`
`2043`		`-/// Produces no rows: An empty relation with an empty schema`
	`2043`	`+/// Relationship produces 0 or 1 placeholder rows with specified output schema`
	`2044`	+/// In most cases the output schema for `EmptyRelation` would be empty,
	`2045`	`+/// however, it can be non-empty typically for optimizer rules`
`2044`	`2046`	`#[derive(Debug, Clone, PartialEq, Eq, Hash)]`
`2045`	`2047`	`pub struct EmptyRelation {`
`2046`	`2048`	`/// Whether to produce a placeholder row`