Add additional docstring comments to from_plan

datafusion/src/optimizer/utils.rs

@@ -111,7 +111,21 @@ pub fn optimize_children(
     from_plan(plan, &new_exprs, &new_inputs)
 }
 
-/// Returns a new logical plan based on the original one with inputs and expressions replaced
+/// Returns a new logical plan based on the original one with inputs
+/// and expressions replaced.
+///
+/// The exprs correspond to the same order of expressions returned by
+/// `LogicalPlan::expressions`. This function is used in optimizers in
+/// the following way:
+///
+///
+/// ```norun
+/// let new_inputs = optimize_children(..., plan, props);
+/// let exprs = plan.expressions();
+/// // potentially rewrite exprs
+/// let rewritten_exprs = rewrite_exprs(exprs);
+/// let new_plan = from_plan(&plan, rewritten_exprs, new_inputs)
+/// ```
 pub fn from_plan(
     plan: &LogicalPlan,
     expr: &[Expr],