alamb commented on code in PR #10410:
URL: https://github.com/apache/datafusion/pull/10410#discussion_r1595383012
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datafusion/expr/src/logical_plan/plan.rs:
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@@ -467,6 +468,200 @@ impl LogicalPlan {
self.with_new_exprs(self.expressions(), inputs.to_vec())
}
+ /// Recomputes schema and type information for this LogicalPlan if needed.
+ ///
+ /// Some `LogicalPlan`s may need to recompute their schema if the number or
+ /// type of expressions have been changed (for example due to type
+ /// coercion). For example [`LogicalPlan::Projection`]s schema depends on
+ /// its expressions.
+ ///
+ /// Some `LogicalPlan`s schema is unaffected by any changes to their
+ /// expressions. For example [`LogicalPlan::Filter`] schema is always the
+ /// same as its input schema.
+ ///
+ /// # Return value
+ /// Returns an error if there is some issue recomputing the schema.
+ ///
+ /// # Notes
+ ///
+ /// * Does not recursively recompute schema for input (child) plans.
+ pub fn recompute_schema(self) -> Result<Self> {
Review Comment:
The key difference is that to use `new_with_expr` it requires providing a
copy (`Vec<Expr>` and `Vec<LogicalPlan>`) where as this function can be used
after modifying the Exprs (or children) via methods such as `map_children` and
`map_expressions`
Avoiding those copies is a key part of improve planning performance in PRs
like https://github.com/apache/datafusion/pull/10356 (the change is basically
to stop copying)
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