feat(Datum): allow to cast from Double to Float

Author: Artem Novikov

crates/iceberg/src/spec/values/datum.rs

@@ -1146,6 +1146,9 @@ impl Datum {
                     (PrimitiveLiteral::String(val), _, PrimitiveType::Timestamptz) => {
                         Datum::timestamptz_from_str(val)
                     }
+                    (PrimitiveLiteral::Double(val), _, PrimitiveType::Float) => {
+                        Ok(Datum::float(**val as f32))
+                    }
 
                     // TODO: implement more type conversions
                     (_, self_type, target_type) if self_type == target_type => Ok(self),

crates/iceberg/src/spec/values/tests.rs

@@ -1352,3 +1352,25 @@ fn test_date_from_json_as_number() {
 
     // Both formats should produce the same Literal value
 }
+
+#[test]
+fn test_iceberg_double_convert_to_float() {
+    let test_data = [
+        (Datum::double(-f64::NAN), Datum::float(-f32::NAN)),
+        (Datum::double(-f64::INFINITY), Datum::float(-f32::INFINITY)),
+        (Datum::double(f64::MIN), Datum::float(-f32::INFINITY)),
+        (Datum::double(f32::MIN as f64), Datum::float(f32::MIN)),
+        (Datum::double(-1.0), Datum::float(-1.0)),
+        (Datum::double(-0.0), Datum::float(-0.0)),
+        (Datum::double(0.0), Datum::float(0.0)),
+        (Datum::double(1.0), Datum::float(1.0)),
+        (Datum::double(f32::MAX as f64), Datum::float(f32::MAX)),
+        (Datum::double(f64::MAX), Datum::float(f32::INFINITY)),
+        (Datum::double(f64::INFINITY), Datum::float(f32::INFINITY)),
+        (Datum::double(f64::NAN), Datum::float(f32::NAN)),
+    ];
+    for (datum, expected) in test_data {
+        let result = datum.to(&Primitive(PrimitiveType::Float)).unwrap();
+        assert_eq!(result, expected);
+    }
+}