!2398 Bug in Slice when multiple rows are used

Merge pull request !2398 from h.farahat/slice_bug

mindspore/ccsrc/dataset/kernels/data/slice_op.cc

@@ -33,8 +33,8 @@ Status SliceOp::Compute(const std::shared_ptr<Tensor> &input, std::shared_ptr<Te
   // if slice object was provided, indices should be empty. Generate indices from the slice object.
   if (slice_.valid() && indices_.empty()) {
     dsize_t len = input->shape()[0];
-    indices_ = slice_.Indices(len);
-    return input->Slice(output, indices_);
+    std::vector<dsize_t> indices = slice_.Indices(len);
+    return input->Slice(output, indices);
   }
 
   // if indices are not empty, slices should be invalid, use indices_ to slice

tests/ut/python/dataset/test_slice_op.py

@@ -80,6 +80,22 @@ def test_slice_slice_obj_3s():
     slice_compare([1, 2, 3, 4, 5], slice(2, 5, 3))
 
 
+def test_slice_multiple_rows():
+    dataset = [[1, 2], [3, 4, 5], [1], [1, 2, 3, 4, 5, 6, 7]]
+
+    def gen():
+        for row in dataset:
+            yield (np.array(row),)
+
+    data = ds.GeneratorDataset(gen, column_names=["col"])
+    indexing = slice(0, 4)
+    data = data.map(operations=ops.Slice(indexing))
+    for i, d in enumerate(data):
+        array = np.array(dataset[i])
+        array = array[indexing]
+        np.testing.assert_array_equal(array, d[0])
+
+
 def test_slice_slice_obj_3s_double():
     slice_compare([1., 2., 3., 4., 5.], slice(0, 2, 1))
     slice_compare([1., 2., 3., 4., 5.], slice(0, 4, 1))
@@ -217,3 +233,4 @@ if __name__ == "__main__":
     test_slice_slice_obj_1s_str()
     test_slice_slice_obj_neg_str()
     test_slice_exceptions_str()
+    test_slice_multiple_rows()