Add reference

Author: adriangb

datafusion/physical-expr/src/expressions/dynamic_filters.rs

@@ -32,6 +32,10 @@ use datafusion_expr::ColumnarValue;
 use datafusion_physical_expr_common::physical_expr::{DynEq, DynHash};
 
 /// A dynamic [`PhysicalExpr`] that can be updated by anyone with a reference to it.
+/// 
+/// Any `ExecutionPlan` that uses this expression and holds a reference to it internally should probably also
+/// implement `ExecutionPlan::reset_state` to remain compatible with recursive queries and other situations where
+/// the same `ExecutionPlan` is reused with different data.
 #[derive(Debug)]
 pub struct DynamicFilterPhysicalExpr {
     /// The original children of this PhysicalExpr, if any.
@@ -120,6 +124,10 @@ impl DynamicFilterPhysicalExpr {
     /// Generally the important bit is that the *leaf children that reference columns
     /// do not change* since those will be used to determine what columns need to read or projected
     /// when evaluating the expression.
+    /// 
+    /// Any `ExecutionPlan` that uses this expression and holds a reference to it internally should probably also
+    /// implement `ExecutionPlan::reset_state` to remain compatible with recursive queries and other situations where
+    /// the same `ExecutionPlan` is reused with different data.
     ///
     /// [`collect_columns`]: crate::utils::collect_columns
     pub fn new(