fix(datatypes): preserve series frame field names

Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>

src/datatypes/src/series/frame.rs

@@ -12,8 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//! Finite Arrow batches for raw series chunks. Field names are ordinal (`f0`, `f1`, ...);
-//! callers bind those positions to their logical names, which this frame cannot authenticate.
+//! Finite Arrow batches for raw series chunks. Field names preserve the logical series schema in order.
 
 #[cfg(test)]
 mod tests;
@@ -50,7 +49,7 @@ pub enum RawLabelMode {
     Explicit,
 }
 
-/// Builds the typed schema for a raw frame using ordinal domain fields.
+/// Builds the typed schema for a raw frame, preserving logical field names and order.
 pub fn raw_series_frame_schema(schema: &SeriesSchema, mode: RawLabelMode) -> Result<SchemaRef> {
     if schema.eval_grid.is_some() {
         return invalid_series("raw series schema cannot have an evaluation grid");
@@ -88,8 +87,7 @@ pub fn raw_series_frame_schema(schema: &SeriesSchema, mode: RawLabelMode) -> Res
     let fields: Fields = schema
         .fields
         .iter()
-        .enumerate()
-        .map(|(i, _)| Field::new(format!("f{i}"), payload.clone(), false))
+        .map(|field| Field::new(field.name.as_ref(), payload.clone(), false))
         .collect();
     let mut columns = vec![
         Field::new("read_key", DataType::Binary, false),

src/datatypes/src/series/frame/tests.rs

@@ -339,6 +339,58 @@ fn sliced_histogram_frames_densify_without_duplicating_shared_table() {
     );
 }
 
+#[test]
+fn raw_frame_field_names_bind_payloads_to_their_schema() {
+    let schema = test_schema(&["cpu_usage", "cpu_idle"]);
+    let fields = SeriesFields::try_from_vec(vec![
+        Samples::from_float(Float64Array::from(vec![Some(1.0), Some(2.0)])),
+        Samples::from_float(Float64Array::from(vec![Some(10.0), Some(20.0)])),
+    ])
+    .unwrap();
+
+    for mode in [RawLabelMode::Key, RawLabelMode::Explicit] {
+        let metric = (mode == RawLabelMode::Explicit).then(|| metric(Some("host"), &[]));
+        let chunk = RawSeriesChunk::try_new(
+            &schema,
+            Buffer::from(vec![0xaa_u8]),
+            metric,
+            RawTimeAxis::try_new(vec![100, 200].into()).unwrap(),
+            fields.clone(),
+            true,
+        )
+        .unwrap();
+        let batch = &pack_raw_series_chunk(&schema, mode, &chunk).unwrap()[0];
+        let payloads = batch
+            .column(3)
+            .as_any()
+            .downcast_ref::<StructArray>()
+            .unwrap();
+        assert_eq!(
+            payloads
+                .fields()
+                .iter()
+                .map(|field| field.name().as_str())
+                .collect::<Vec<_>>(),
+            ["cpu_usage", "cpu_idle"]
+        );
+
+        let decoded = unpack_raw_series_frame(&schema, mode, batch).unwrap();
+        assert_eq!(decoded[0].read_key.as_slice(), &[0xaa]);
+        assert!(decoded[0].is_last);
+        let RawTimeAxis::Explicit(times) = &decoded[0].time;
+        assert_eq!(times.as_ref(), &[100, 200]);
+        assert_float_bits(decoded[0].fields.get(0).unwrap(), &[Some(1.0), Some(2.0)]);
+        assert_float_bits(decoded[0].fields.get(1).unwrap(), &[Some(10.0), Some(20.0)]);
+
+        assert!(
+            unpack_raw_series_frame(&test_schema(&["cpu_idle", "cpu_usage"]), mode, batch).is_err()
+        );
+        assert!(
+            unpack_raw_series_frame(&test_schema(&["cpu_usage", "cpu_busy"]), mode, batch).is_err()
+        );
+    }
+}
+
 #[test]
 fn schema_and_key_explicit_round_trips_preserve_identity_and_bits() {
     let schema = test_schema(&["value"]);
@@ -400,7 +452,7 @@ fn schema_and_key_explicit_round_trips_preserve_identity_and_bits() {
             ),
             Field::new(
                 "fields",
-                DataType::Struct(vec![Field::new("f0", payload, false)].into()),
+                DataType::Struct(vec![Field::new("value", payload, false)].into()),
                 false,
             ),
         ],