GH-38211: [MATLAB] Add support for creating an empty arrow.tabular.RecordBatch by calling arrow.recordBatch with no input arguments (#47060)

sgilmore10 · web-flow · commit a23c2c7f5268 · 2025-07-10T15:00:43.000-04:00
### Rationale for this change Currently, the `arrow.table` construction function will return an empty `arrow.tabular.Table` if no input arguments are passed to the function. However, `arrow.recordBatch` throws an error in this case. We should consider making `arrow.recordBatch` behave consistently with `arrow.table` in this case. This should be relatively straightforward to implement. We can just set the input argument `T` to default to `table.empty(0,0)` in the `arguments` block of the `recordBatch` function, in the same way that `arrow.table` does: https://github.com/apache/arrow/blob/73454b7040fbea3a187c1bfabd7ea02d46ca3c41/matlab/src/matlab/%2Barrow/table.m#L21 ### What changes are included in this PR? Updated the `arrow.recordBatch` function to return an `arrow.tabular.RecordBatch` instance with zero columns and zero rows if called with zero input arguments. Before this change, the `arrow.recordBatch` function would throw an error if called with zero input arguments. **Example Usage:** ```matlab >> rb = arrow.recordBatch() rb = Arrow RecordBatch with 0 rows and 0 columns ``` ### Are these changes tested? Yes. Added a new test case to `tRecordBatch` called `ConvenienceConstructorZeroArguments`. ### Are there any user-facing changes? Yes. Users can now call `arrow.recordBatch` with zero input arguments. * GitHub Issue: #38211 Authored-by: Sarah Gilmore <sgilmore@mathworks.com> Signed-off-by: Sarah Gilmore <sgilmore@mathworks.com>
diff --git a/matlab/src/matlab/+arrow/recordBatch.m b/matlab/src/matlab/+arrow/recordBatch.m
@@ -16,7 +16,7 @@
 % permissions and limitations under the License.
 function rb = recordBatch(T)
     arguments
-        T table
+        T table = table.empty(0, 0)
     end
 
     arrowArrays = arrow.tabular.internal.decompose(T);
diff --git a/matlab/test/arrow/tabular/tRecordBatch.m b/matlab/test/arrow/tabular/tRecordBatch.m
@@ -25,6 +25,17 @@ function Basic(tc)
             tc.verifyEqual(className, "arrow.tabular.RecordBatch");
         end
 
+        function ConvenienceConstructorZeroArguments(tc)
+            % Verify the arrow.recordBatch function returns an 
+            % arrow.tabular.RecordBatch instance with zero rows and zero
+            % columns if called with zero input arguments.
+            recordBatch = arrow.recordBatch();
+            className = string(class(recordBatch));
+            tc.verifyEqual(className, "arrow.tabular.RecordBatch");
+            tc.verifyEqual(recordBatch.NumRows, int64(0));
+            tc.verifyEqual(recordBatch.NumColumns, int32(0));
+        end
+
         function SupportedTypes(tc)
             % Create a table all supported MATLAB types.
             import arrow.internal.test.tabular.createTableWithSupportedTypes
