[GitHub] [arrow-datafusion] alamb commented on a change in pull request #381: Function to create `ArrayRef` from an iterator of ScalarValues

[GitBox <gi...@apache.org>]

alamb commented on a change in pull request #381:
URL: https://github.com/apache/arrow-datafusion/pull/381#discussion_r637525780



##########
File path: datafusion/src/scalar.rs
##########
@@ -283,6 +283,155 @@ impl ScalarValue {
         self.to_array_of_size(1)
     }
 
+    /// Converts an iterator of references [`ScalarValue`] into an [`ArrayRef`]
+    /// corresponding to those values. For example,
+    ///
+    /// Returns an error if the iterator is empty or if the
+    /// [`ScalarValue`]s are not all the same type
+    ///
+    /// Example
+    /// ```
+    /// use datafusion::scalar::ScalarValue;
+    /// use arrow::array::{ArrayRef, BooleanArray};
+    ///
+    /// let scalars = vec![
+    ///   ScalarValue::Boolean(Some(true)),
+    ///   ScalarValue::Boolean(None),
+    ///   ScalarValue::Boolean(Some(false)),
+    /// ];
+    ///
+    /// // Build an Array from the list of ScalarValues
+    /// let array = ScalarValue::iter_to_array(scalars.iter())
+    ///   .unwrap();
+    ///
+    /// let expected: ArrayRef = std::sync::Arc::new(
+    ///   BooleanArray::from(vec![
+    ///     Some(true),
+    ///     None,
+    ///     Some(false)
+    ///   ]
+    /// ));
+    ///
+    /// assert_eq!(&array, &expected);
+    /// ```
+    pub fn iter_to_array<'a>(
+        scalars: impl IntoIterator<Item = &'a ScalarValue>,
+    ) -> Result<ArrayRef> {
+        let mut scalars = scalars.into_iter().peekable();
+
+        // figure out the type based on the first element
+        let data_type = match scalars.peek() {

Review comment:
       Yeah -- this confused me a little -- it is convenient that `ScalarValue` is always typed even when it is `None` 




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