Short circuit ApplyFunctionRewrites if there are no function rewrites

Author: gruuya

datafusion/optimizer/src/analyzer/function_rewrite.rs

@@ -85,6 +85,11 @@ impl AnalyzerRule for ApplyFunctionRewrites {
     }
 
     fn analyze(&self, plan: LogicalPlan, options: &ConfigOptions) -> Result<LogicalPlan> {
+        if self.function_rewrites.is_empty() {
+            // No need to walk the plan tree since there's nothing to rewrite
+            return Ok(plan);
+        }
+
         plan.transform_up_with_subqueries(|plan| self.rewrite_plan(plan, options))
             .map(|res| res.data)
     }