Adding is_null datatype shortcut method (apache#5157)

arrow-schema/src/datatype.rs

@@ -350,23 +350,27 @@ impl DataType {
  }
 
  /// Returns true if this type is floating: (Float*).
+ #[inline]
  pub fn is_floating(&self) -> bool {
  use DataType::*;
  matches!(self, Float16 | Float32 | Float64)
  }
 
  /// Returns true if this type is integer: (Int*, UInt*).
+ #[inline]
  pub fn is_integer(&self) -> bool {
  self.is_signed_integer() || self.is_unsigned_integer()
  }
 
  /// Returns true if this type is signed integer: (Int*).
+ #[inline]
  pub fn is_signed_integer(&self) -> bool {
  use DataType::*;
  matches!(self, Int8 | Int16 | Int32 | Int64)
  }
 
  /// Returns true if this type is unsigned integer: (UInt*).
+ #[inline]
  pub fn is_unsigned_integer(&self) -> bool {
  use DataType::*;
  matches!(self, UInt8 | UInt16 | UInt32 | UInt64)
@@ -387,6 +391,7 @@ impl DataType {
 
  /// Returns true if this type is nested (List, FixedSizeList, LargeList, Struct, Union,
  /// or Map), or a dictionary of a nested type
+ #[inline]
  pub fn is_nested(&self) -> bool {
  use DataType::*;
  match self {
@@ -398,6 +403,13 @@ impl DataType {
  }
  }
 
+ /// Returns true if this type is DataType::Null.
+ #[inline]
+ pub fn is_null(&self) -> bool {
+ use DataType::*;
+ matches!(self, Null)
+ }
+
  /// Compares the datatype with another, ignoring nested field names
  /// and metadata.
  pub fn equals_datatype(&self, other: &DataType) -> bool {
@@ -855,6 +867,12 @@ mod tests {
  assert!(!DataType::is_floating(&DataType::Int32));
  }
 
+ #[test]
+ fn test_datatype_is_null() {
+ assert!(DataType::is_null(&DataType::Null));
+ assert!(!DataType::is_null(&DataType::Int32));
+ }
+
  #[test]
  fn size_should_not_regress() {
  assert_eq!(std::mem::size_of::<DataType>(), 24);