Raising an error when trying to get data for a non-existent label

Author: Sean Underwood

hnswlib/hnswalg.h

@@ -633,7 +633,13 @@ namespace hnswlib {
         template<typename data_t>
         std::vector<data_t> getDataByLabel(labeltype label)
         {
-          tableint label_c = label_lookup_[label];
+          tableint label_c;
+          auto search = label_lookup_.find(label);
+          if (search == label_lookup_.end()) {
+              throw std::runtime_error("Label not found");
+          }
+          label_c = search->second;
+
           char* data_ptrv = getDataByInternalId(label_c);
           size_t dim = *((size_t *) dist_func_param_);
           std::vector<data_t> data;

python_bindings/tests/bindings_test_getdata.py

@@ -0,0 +1,46 @@
+import unittest
+
+
+class RandomSelfTestCase(unittest.TestCase):
+    def testGettingItems(self):
+        import hnswlib
+        import numpy as np
+
+        dim = 16
+        num_elements = 10000
+
+        # Generating sample data
+        data = np.float32(np.random.random((num_elements, dim)))
+        labels = np.arange(0, num_elements)
+
+        # Declaring index
+        p = hnswlib.Index(space='l2', dim=dim)  # possible options are l2, cosine or ip
+
+        # Initing index
+        # max_elements - the maximum number of elements, should be known beforehand
+        #     (probably will be made optional in the future)
+        #
+        # ef_construction - controls index search speed/build speed tradeoff
+        # M - is tightly connected with internal dimensionality of the data
+        #     stronlgy affects the memory consumption
+
+        p.init_index(max_elements=num_elements, ef_construction=100, M=16)
+
+        # Controlling the recall by setting ef:
+        # higher ef leads to better accuracy, but slower search
+        p.set_ef(300)
+
+        p.set_num_threads(4)  # by default using all available cores
+
+        # Before adding anything, getting any labels should fail
+        self.assertRaises(Exception, lambda: p.get_items(labels))
+
+        print("Adding all elements (%d)" % (len(data)))
+        p.add_items(data, labels)
+
+        # After adding them, all labels should be retrievable
+        returned_items = p.get_items(labels)
+        self.assertSequenceEqual(data.tolist(), returned_items)
+
+if __name__ == "__main__":
+    unittest.main()