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new 89efc4a7e0 Minor: Add documentation about LogicalPlan::expressions
(#9698)
89efc4a7e0 is described below
commit 89efc4a7e06bd0295ca72dd6ec5fe987d1ac246b
Author: Andrew Lamb <[email protected]>
AuthorDate: Wed Mar 20 08:58:02 2024 -0400
Minor: Add documentation about LogicalPlan::expressions (#9698)
---
datafusion/expr/src/logical_plan/extension.rs | 9 +++++----
datafusion/expr/src/logical_plan/plan.rs | 14 +++++++++++---
2 files changed, 16 insertions(+), 7 deletions(-)
diff --git a/datafusion/expr/src/logical_plan/extension.rs
b/datafusion/expr/src/logical_plan/extension.rs
index f87ca45f14..bb2c932ce3 100644
--- a/datafusion/expr/src/logical_plan/extension.rs
+++ b/datafusion/expr/src/logical_plan/extension.rs
@@ -53,10 +53,11 @@ pub trait UserDefinedLogicalNode: fmt::Debug + Send + Sync {
/// Return the output schema of this logical plan node.
fn schema(&self) -> &DFSchemaRef;
- /// Returns all expressions in the current logical plan node. This
- /// should not include expressions of any inputs (aka
- /// non-recursively). These expressions are used for optimizer
- /// passes and rewrites.
+ /// Returns all expressions in the current logical plan node. This should
+ /// not include expressions of any inputs (aka non-recursively).
+ ///
+ /// These expressions are used for optimizer
+ /// passes and rewrites. See [`LogicalPlan::expressions`] for more details.
fn expressions(&self) -> Vec<Expr>;
/// A list of output columns (e.g. the names of columns in
diff --git a/datafusion/expr/src/logical_plan/plan.rs
b/datafusion/expr/src/logical_plan/plan.rs
index 08fe338006..05d7ac5394 100644
--- a/datafusion/expr/src/logical_plan/plan.rs
+++ b/datafusion/expr/src/logical_plan/plan.rs
@@ -234,9 +234,17 @@ impl LogicalPlan {
])
}
- /// returns all expressions (non-recursively) in the current
- /// logical plan node. This does not include expressions in any
- /// children
+ /// Returns all expressions (non-recursively) evaluated by the current
+ /// logical plan node. This does not include expressions in any children
+ ///
+ /// The returned expressions do not necessarily represent or even
+ /// contributed to the output schema of this node. For example,
+ /// `LogicalPlan::Filter` returns the filter expression even though the
+ /// output of a Filter has the same columns as the input.
+ ///
+ /// The expressions do contain all the columns that are used by this plan,
+ /// so if there are columns not referenced by these expressions then
+ /// DataFusion's optimizer attempts to optimize them away.
pub fn expressions(self: &LogicalPlan) -> Vec<Expr> {
let mut exprs = vec![];
self.inspect_expressions(|e| {
