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new 31381bfd9 impl Debug for ColumnarValue, add some docs (#3076)
31381bfd9 is described below
commit 31381bfd96f5a22db27cb28a429d570b509c0542
Author: Andrew Lamb <[email protected]>
AuthorDate: Tue Aug 9 08:23:31 2022 -0400
impl Debug for ColumnarValue, add some docs (#3076)
---
datafusion/expr/src/columnar_value.rs | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/datafusion/expr/src/columnar_value.rs
b/datafusion/expr/src/columnar_value.rs
index 4867c0e74..48a29208b 100644
--- a/datafusion/expr/src/columnar_value.rs
+++ b/datafusion/expr/src/columnar_value.rs
@@ -24,8 +24,13 @@ use arrow::record_batch::RecordBatch;
use datafusion_common::ScalarValue;
use std::sync::Arc;
-/// Represents the result from an expression
-#[derive(Clone)]
+/// Represents the result of evaluating an expression: either a single
+/// `ScalarValue` or an [`ArrayRef`].
+///
+/// While a [`ColumnarValue`] can always be converted into an array
+/// for convenience, it is often much more performant to provide an
+/// optimized path for scalar values.
+#[derive(Clone, Debug)]
pub enum ColumnarValue {
/// Array of values
Array(ArrayRef),
@@ -41,7 +46,8 @@ impl ColumnarValue {
}
}
- /// Convert a columnar value into an ArrayRef
+ /// Convert a columnar value into an ArrayRef. [`Self::Scalar`] is
+ /// converted by repeating the same scalar multiple times.
pub fn into_array(self, num_rows: usize) -> ArrayRef {
match self {
ColumnarValue::Array(array) => array,
