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

Author: Artem Novikov

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

@@ -48,6 +48,8 @@ pub(crate) const INT_MAX: i32 = 2147483647;
 pub(crate) const INT_MIN: i32 = -2147483648;
 pub(crate) const LONG_MAX: i64 = 9223372036854775807;
 pub(crate) const LONG_MIN: i64 = -9223372036854775808;
+pub(crate) const FLOAT_MAX: f32 = 3.4028235e38;
+pub(crate) const FLOAT_MIN: f32 = -3.4028235e38;
 
 /// Literal associated with its type. The value and type pair is checked when construction, so the type and value is
 /// guaranteed to be correct when used.
@@ -1109,6 +1111,16 @@ impl Datum {
         })
     }
 
+    fn double_to_float<T: Into<f64> + PartialOrd<f64>>(val: T) -> Datum {
+        if val > FLOAT_MAX as f64 {
+            Datum::new(PrimitiveType::Float, PrimitiveLiteral::AboveMax)
+        } else if val < FLOAT_MIN as f64 {
+            Datum::new(PrimitiveType::Float, PrimitiveLiteral::BelowMin)
+        } else {
+            Datum::float(val.into() as f32)
+        }
+    }
+
     /// Convert the datum to `target_type`.
     pub fn to(self, target_type: &Type) -> Result<Datum> {
         match target_type {
@@ -1146,6 +1158,9 @@ impl Datum {
                     (PrimitiveLiteral::String(val), _, PrimitiveType::Timestamptz) => {
                         Datum::timestamptz_from_str(val)
                     }
+                    (PrimitiveLiteral::Double(val), _, PrimitiveType::Float) => {
+                        Ok(Datum::double_to_float(**val))
+                    }
 
                     // 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 +1352,39 @@ fn test_date_from_json_as_number() {
 
     // Both formats should produce the same Literal value
 }
+
+#[test]
+fn test_iceberg_double_convert_to_float() {
+    let float_below_min = Datum::new(PrimitiveType::Float, PrimitiveLiteral::BelowMin);
+    let float_above_max = Datum::new(PrimitiveType::Float, PrimitiveLiteral::AboveMax);
+
+    let test_data = [
+        (Datum::double(-f64::NAN), Datum::float(-f32::NAN)),
+        (Datum::double(-f64::INFINITY), float_below_min.clone()),
+        (Datum::double(f64::MIN), float_below_min),
+        (Datum::double(f32::MIN as f64), Datum::float(f32::MIN)),
+        (Datum::double(-1.0), Datum::float(-1.0)),
+        (Datum::double(-f64::MIN_POSITIVE), Datum::float(-0.0)),
+        (
+            Datum::double(-f32::MIN_POSITIVE as f64),
+            Datum::float(-f32::MIN_POSITIVE),
+        ),
+        (Datum::double(-0.0), Datum::float(-0.0)),
+        (Datum::double(0.0), Datum::float(0.0)),
+        (Datum::double(f64::MIN_POSITIVE), Datum::float(0.0)),
+        (
+            Datum::double(f32::MIN_POSITIVE as f64),
+            Datum::float(f32::MIN_POSITIVE),
+        ),
+        (Datum::double(1.0), Datum::float(1.0)),
+        (Datum::double(f32::MAX as f64), Datum::float(f32::MAX)),
+        (Datum::double(f64::MAX), float_above_max.clone()),
+        (Datum::double(f64::INFINITY), float_above_max),
+        (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);
+    }
+}