Add NULL literal support for decimal type

Cargo fmt

src/consumer.rs

@@ -620,6 +620,11 @@ fn from_substrait_null(null_type: &Type) -> Result<ScalarValue> {
             r#type::Kind::I16(_) => Ok(ScalarValue::Int16(None)),
             r#type::Kind::I32(_) => Ok(ScalarValue::Int32(None)),
             r#type::Kind::I64(_) => Ok(ScalarValue::Int64(None)),
+            r#type::Kind::Decimal(d) => Ok(ScalarValue::Decimal128(
+                None,
+                d.precision as u8,
+                d.scale as u8,
+            )),
             _ => Err(DataFusionError::NotImplemented(format!(
                 "Unsupported null kind: {:?}",
                 kind

src/producer.rs

@@ -572,8 +572,8 @@ pub fn to_substrait_rex(
                 ScalarValue::Boolean(Some(b)) => Some(LiteralType::Boolean(*b)),
                 ScalarValue::Float32(Some(f)) => Some(LiteralType::Fp32(*f)),
                 ScalarValue::Float64(Some(f)) => Some(LiteralType::Fp64(*f)),
-                ScalarValue::Decimal128(v, p, s) => Some(LiteralType::Decimal(Decimal {
-                    value: v.unwrap().to_le_bytes().to_vec(),
+                ScalarValue::Decimal128(Some(v), p, s) => Some(LiteralType::Decimal(Decimal {
+                    value: v.to_le_bytes().to_vec(),
                     precision: *p as i32,
                     scale: *s as i32,
                 })),
@@ -628,6 +628,14 @@ fn try_to_substrait_null(v: &ScalarValue) -> Result<LiteralType> {
                 nullability: default_nullability,
             })),
         })),
+        ScalarValue::Decimal128(None, p, s) => Ok(LiteralType::Null(substrait::protobuf::Type {
+            kind: Some(r#type::Kind::Decimal(r#type::Decimal {
+                scale: *s as i32,
+                precision: *p as i32,
+                type_variation_reference: default_type_ref,
+                nullability: default_nullability,
+            })),
+        })),
         // TODO: Extend support for remaining data types
         _ => Err(DataFusionError::NotImplemented(format!(
             "Unsupported literal: {:?}",

tests/roundtrip.rs

@@ -79,6 +79,11 @@ mod tests {
         roundtrip("SELECT * FROM data WHERE b > 2.5").await
     }
 
+    #[tokio::test]
+    async fn null_decimal_literal() -> Result<()> {
+        roundtrip("SELECT * FROM data WHERE b = NULL").await
+    }
+
     #[tokio::test]
     async fn simple_distinct() -> Result<()> {
         test_alias(