[GitHub] [arrow-datafusion] alamb commented on a change in pull request #303: add random SQL function

[GitBox]

alamb commented on a change in pull request #303:
URL: https://github.com/apache/arrow-datafusion/pull/303#discussion_r630407771



##########
File path: datafusion/src/physical_plan/functions.rs
##########
@@ -1373,20 +1370,26 @@ impl PhysicalExpr for ScalarFunctionExpr {
     }
 
     fn evaluate(&self, batch: &RecordBatch) -> Result<ColumnarValue> {
-        // evaluate the arguments
-        let inputs = self
-            .args
-            .iter()
-            .map(|e| e.evaluate(batch))
-            .collect::<Result<Vec<_>>>()?;
+        // evaluate the arguments, if there are no arguments we'll instead 
pass in a null array of
+        // batch size (as a convention)
+        let inputs = match self.args.len() {
+            0 => vec![ColumnarValue::Array(Arc::new(NullArray::new(

Review comment:
       I like the idea of using `NullArray` too, but generally agree with 
@Dandandan  that both are somewhat hacky ways to handle zero argument functions 
by passing a "fake" argument




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