Added remaining scalars and improved API.

src/compute/aggregate/sum.rs

@@ -118,6 +118,32 @@ macro_rules! dyn_sum {
     }};
 }
 
+pub fn can_sum(data_type: &DataType) -> bool {
+    use DataType::*;
+    matches!(
+        data_type,
+        Int8 | Int16
+            | Date32
+            | Time32(_)
+            | Interval(IntervalUnit::YearMonth)
+            | Int64
+            | Date64
+            | Time64(_)
+            | Timestamp(_, _)
+            | Duration(_)
+            | UInt8
+            | UInt16
+            | UInt32
+            | UInt64
+            | Float32
+            | Float64
+    )
+}
+
+/// Returns the sum of all elements in `array` as a [`Scalar`] of the same physical
+/// and logical types as `array`.
+/// # Error
+/// Errors iff the operation is not supported.
 pub fn sum(array: &dyn Array) -> Result<Box<dyn Scalar>> {
     Ok(match array.data_type() {
         DataType::Int8 => dyn_sum!(i8, array),
@@ -158,7 +184,16 @@ mod tests {
     #[test]
     fn test_primitive_array_sum() {
         let a = Int32Array::from_slice(&[1, 2, 3, 4, 5]);
-        assert_eq!(15, sum(&a).unwrap());
+        assert_eq!(
+            &PrimitiveScalar::<i32>::from(Some(15)) as &dyn Scalar,
+            sum(&a).unwrap().as_ref()
+        );
+
+        let a = a.to(DataType::Date32);
+        assert_eq!(
+            &PrimitiveScalar::<i32>::from(Some(15)).to(DataType::Date32) as &dyn Scalar,
+            sum(&a).unwrap().as_ref()
+        );
     }
 
     #[test]

src/lib.rs

@@ -4,6 +4,7 @@ pub mod bitmap;
 pub mod buffer;
 mod endianess;
 pub mod error;
+#[cfg(feature = "compute")]
 pub mod scalar;
 pub mod trusted_len;
 pub mod types;

src/scalar/README.md

@@ -10,7 +10,7 @@ There are three reasons:
 * forward-compatibility: a new entry on an `enum` is backward-incompatible
 * do not expose implementation details to users (reduce the surface of the public API)
 
-### `Scalar` should contain nullability information
+### `Scalar` MUST contain nullability information
 
 This is to be aligned with the general notion of arrow's `Array`.
 

src/scalar/binary.rs

@@ -0,0 +1,50 @@
+use crate::{array::*, buffer::Buffer, datatypes::DataType};
+
+use super::Scalar;
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct BinaryScalar<O: Offset> {
+    value: Buffer<u8>,
+    is_valid: bool,
+    phantom: std::marker::PhantomData<O>,
+}
+
+impl<O: Offset> BinaryScalar<O> {
+    #[inline]
+    pub fn new(v: Option<&[u8]>) -> Self {
+        let is_valid = v.is_some();
+        O::from_usize(v.map(|x| x.len()).unwrap_or_default()).expect("Too large");
+        let value = Buffer::from(v.unwrap_or(&[]));
+        Self {
+            value,
+            is_valid,
+            phantom: std::marker::PhantomData,
+        }
+    }
+
+    #[inline]
+    pub fn value(&self) -> &[u8] {
+        self.value.as_slice()
+    }
+}
+
+impl<O: Offset> Scalar for BinaryScalar<O> {
+    #[inline]
+    fn as_any(&self) -> &dyn std::any::Any {
+        self
+    }
+
+    #[inline]
+    fn is_valid(&self) -> bool {
+        self.is_valid
+    }
+
+    #[inline]
+    fn data_type(&self) -> &DataType {
+        if O::is_large() {
+            &DataType::LargeBinary
+        } else {
+            &DataType::Binary
+        }
+    }
+}

src/scalar/boolean.rs

@@ -0,0 +1,42 @@
+use crate::datatypes::DataType;
+
+use super::Scalar;
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct BooleanScalar {
+    value: bool,
+    is_valid: bool,
+}
+
+impl BooleanScalar {
+    #[inline]
+    pub fn new(v: Option<bool>) -> Self {
+        let is_valid = v.is_some();
+        Self {
+            value: v.unwrap_or_default(),
+            is_valid,
+        }
+    }
+
+    #[inline]
+    pub fn value(&self) -> bool {
+        self.value
+    }
+}
+
+impl Scalar for BooleanScalar {
+    #[inline]
+    fn as_any(&self) -> &dyn std::any::Any {
+        self
+    }
+
+    #[inline]
+    fn is_valid(&self) -> bool {
+        self.is_valid
+    }
+
+    #[inline]
+    fn data_type(&self) -> &DataType {
+        &DataType::Boolean
+    }
+}

src/scalar/equal.rs

@@ -0,0 +1,115 @@
+use super::*;
+
+impl PartialEq for dyn Scalar {
+    fn eq(&self, other: &Self) -> bool {
+        equal(self, other)
+    }
+}
+
+macro_rules! dyn_eq {
+    ($ty:ty, $lhs:expr, $rhs:expr) => {{
+        let lhs = $lhs
+            .as_any()
+            .downcast_ref::<PrimitiveScalar<$ty>>()
+            .unwrap();
+        let rhs = $rhs
+            .as_any()
+            .downcast_ref::<PrimitiveScalar<$ty>>()
+            .unwrap();
+        lhs == rhs
+    }};
+}
+
+fn equal(lhs: &dyn Scalar, rhs: &dyn Scalar) -> bool {
+    if lhs.data_type() != rhs.data_type() {
+        return false;
+    }
+
+    match lhs.data_type() {
+        DataType::Null => {
+            let lhs = lhs.as_any().downcast_ref::<NullScalar>().unwrap();
+            let rhs = rhs.as_any().downcast_ref::<NullScalar>().unwrap();
+            lhs == rhs
+        }
+        DataType::Boolean => {
+            let lhs = lhs.as_any().downcast_ref::<BooleanScalar>().unwrap();
+            let rhs = rhs.as_any().downcast_ref::<BooleanScalar>().unwrap();
+            lhs == rhs
+        }
+        DataType::UInt8 => {
+            dyn_eq!(u8, lhs, rhs)
+        }
+        DataType::UInt16 => {
+            dyn_eq!(u16, lhs, rhs)
+        }
+        DataType::UInt32 => {
+            dyn_eq!(u32, lhs, rhs)
+        }
+        DataType::UInt64 => {
+            dyn_eq!(u64, lhs, rhs)
+        }
+        DataType::Int8 => {
+            dyn_eq!(i8, lhs, rhs)
+        }
+        DataType::Int16 => {
+            dyn_eq!(i16, lhs, rhs)
+        }
+        DataType::Int32
+        | DataType::Date32
+        | DataType::Time32(_)
+        | DataType::Interval(IntervalUnit::YearMonth) => {
+            dyn_eq!(i32, lhs, rhs)
+        }
+        DataType::Int64
+        | DataType::Date64
+        | DataType::Time64(_)
+        | DataType::Timestamp(_, _)
+        | DataType::Duration(_) => {
+            dyn_eq!(i64, lhs, rhs)
+        }
+        DataType::Decimal(_, _) => {
+            dyn_eq!(i128, lhs, rhs)
+        }
+        DataType::Interval(IntervalUnit::DayTime) => {
+            dyn_eq!(days_ms, lhs, rhs)
+        }
+        DataType::Float16 => unreachable!(),
+        DataType::Float32 => {
+            dyn_eq!(f32, lhs, rhs)
+        }
+        DataType::Float64 => {
+            dyn_eq!(f64, lhs, rhs)
+        }
+        DataType::Utf8 => {
+            let lhs = lhs.as_any().downcast_ref::<Utf8Scalar<i32>>().unwrap();
+            let rhs = rhs.as_any().downcast_ref::<Utf8Scalar<i32>>().unwrap();
+            lhs == rhs
+        }
+        DataType::LargeUtf8 => {
+            let lhs = lhs.as_any().downcast_ref::<Utf8Scalar<i64>>().unwrap();
+            let rhs = rhs.as_any().downcast_ref::<Utf8Scalar<i64>>().unwrap();
+            lhs == rhs
+        }
+        DataType::Binary => {
+            let lhs = lhs.as_any().downcast_ref::<BinaryScalar<i32>>().unwrap();
+            let rhs = rhs.as_any().downcast_ref::<BinaryScalar<i32>>().unwrap();
+            lhs == rhs
+        }
+        DataType::LargeBinary => {
+            let lhs = lhs.as_any().downcast_ref::<BinaryScalar<i64>>().unwrap();
+            let rhs = rhs.as_any().downcast_ref::<BinaryScalar<i64>>().unwrap();
+            lhs == rhs
+        }
+        DataType::List(_) => {
+            let lhs = lhs.as_any().downcast_ref::<ListScalar<i32>>().unwrap();
+            let rhs = rhs.as_any().downcast_ref::<ListScalar<i32>>().unwrap();
+            lhs == rhs
+        }
+        DataType::LargeList(_) => {
+            let lhs = lhs.as_any().downcast_ref::<ListScalar<i64>>().unwrap();
+            let rhs = rhs.as_any().downcast_ref::<ListScalar<i64>>().unwrap();
+            lhs == rhs
+        }
+        _ => unimplemented!(),
+    }
+}

src/scalar/list.rs

@@ -0,0 +1,62 @@
+use std::any::Any;
+use std::sync::Arc;
+
+use crate::{array::*, datatypes::DataType};
+
+use super::Scalar;
+
+/// The scalar equivalent of [`ListArray`]. Like [`ListArray`], this struct holds a dynamically-typed
+/// [`Array`]. The only difference is that this has only one element.
+#[derive(Debug, Clone)]
+pub struct ListScalar<O: Offset> {
+    values: Arc<dyn Array>,
+    is_valid: bool,
+    phantom: std::marker::PhantomData<O>,
+    data_type: DataType,
+}
+
+impl<O: Offset> PartialEq for ListScalar<O> {
+    fn eq(&self, other: &Self) -> bool {
+        (self.data_type == other.data_type)
+            && (self.is_valid == other.is_valid)
+            && (self.is_valid && (self.values.as_ref() == other.values.as_ref()))
+    }
+}
+
+pub enum ListScalarNew {
+    Array(Arc<dyn Array>),
+    DataType(DataType),
+}
+
+impl<O: Offset> ListScalar<O> {
+    #[inline]
+    pub fn new(data_type: DataType, values: Option<Arc<dyn Array>>) -> Self {
+        let (is_valid, values) = match values {
+            Some(values) => (true, values),
+            None => {
+                let data_type = ListArray::<O>::get_child_type(&data_type).clone();
+                (false, new_empty_array(data_type).into())
+            }
+        };
+        Self {
+            values,
+            is_valid,
+            phantom: std::marker::PhantomData,
+            data_type,
+        }
+    }
+}
+
+impl<O: Offset> Scalar for ListScalar<O> {
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn is_valid(&self) -> bool {
+        self.is_valid
+    }
+
+    fn data_type(&self) -> &DataType {
+        &self.data_type
+    }
+}